Krita. I had a uni licence for Photoshop for years, even took a Photoshop course but still kept using Krita. It has an intuitive UI and all the tools I'll ever need.
RStudio+R is way better than any of its proprietary alternatives.
Blender. I'm no 3D modling expert but it does everything I as a hobbyist want to do with it and so much more. Nowadays, the UI is pretty decent, too.
Finally, the Lagrange browser is really good. The gemini protocol is kinda niche though, but if you're interested it's unreasonably pretty, well optimized and has a great UX. The guy who maintains it really puts his heart and soul into it.
Practically every single FOSS application I use is highly useful to me, and of course, free, so I'll just list them all here.
Immich - A full-featured replacement for Google Photos, has a sleek UI, face detection, albums, a timeline, etc.
Paperless-ngx - Document management system, saves me a ton of paper hoarding, and makes everything easily searchable with OCR.
Syncthing - Simple file synchronization between my devices, on my terms. Doesn't share data with big tech companies about my files, and hooks up extremely fast P2P connections that beat cloud-based services by a long shot.
Metube & Seal - Simple interfaces for downloading with yt-dlp, can download from YouTube, but also many other sites. Doesn't spam you with popup ads or junk redirects like those "youtube downloader" type sites. Seal is my favorite of the two, but is only on Android.
Image Toolbox - Insanely feature-packed app for doing practically anything you could want to an image. Converting formats, clearing EXIF data, removing backgrounds, feature-packed editing, OCR, convert to SVG, create color palettes, converting PDFs to images, decode and encode Base64 to and from images, extract frames from gifs, encrypt & decrypt files, make zip files, and a lot more. All local.
Rustdesk - No-nonsense remote desktop, tons of features, simple file transfer, cross-platform compatibility, and P2P communication without needing a third party server if you so choose.
LibreOffice - Essentially everything you'd get with Office 365 (e.g. Word, Excel, PowerPoint) but without the $150 price point. Compatible with the same file formats, and has the same functionality.
Cashew - Feature rich financial app for budgeting, tracking purchases, saving for goals, etc. Doesn't have automatic import, but I find that manually putting every transaction in keeps me aware of my spending much better than before, so for me it's quite worth it. Install directly from the APK, or use on web though. The version on the app stores has some features locked behind a paywall.
Linkwarden - Bookmark manager with cross-platform support, a web interface, automatic tagging, automatic archiving of any saved links in multiple formats, collaborative sharing capabilities, and more. It's free, but you can also pay $3/mo if you want them to host it for you.
Edit: And Umbrel (on Raspberry Pi) if you want to host things more easily. Basically just a much more hands-off, user-friendly docker for people who don't want to tinker as much.
Edit 2: Non-FOSS, but Obsidian is the best note taking app I've ever used. Great selection of community-made plugins (which are FOSS) for additional functionality, and all notes are in standard cross-software-compatible Markdown. No locked-in proprietary formats.
I think Blender is a very honorable mention, especially since the team that makes the software has also used it to make some really impressive short films, such as Big Buck Bunny. Who knows, maybe some indie studio can use it to make some truly wonderful stuff (and I wouldn't be surprised if that was the case).
Borg backup, powerful backup software for self-hosted oriented users or enterprise automation.
proxmox, hypervisor that is performant and easy to setup for simple and complex virtualization needs.
bitwarden (combined with vaultwarden self-host), password management, secrets management, and available on basically all platforms and browsers. Self hosting your vault gives you peace of mind over who has your most sensitive data.
obsidian, a great notes app with polished cross platform applications that don’t do any funky proprietary storage shenanigans. Files are files and folders are folders.
kate (and most of the KDE suite), premiere Linux desktop environment suitable for customization and all the expected luxuries user would expect from windows or macOS. Kate specifically is a noticeable modern upgrade over notepad++ and rivals VSCode for programmers.
OrganicMaps, all the trails I've been to so far in the US are available for offline navigation. No need to precache via gmaps and pray it won't get deleted
Edit: OpenStreetMap which powers this is what AllTrails uses, but I'm not sure if they contribute back or not
It tracks devices around on a map and records stats about them. Used by fleet managers to monitor thousands of vehicles simultaneous, and also people like me with just two. The interface is a little quirky, but otherwise it's a very solid and capable program. It shows a web map with live positions of the devices, battery state, speed, direction and other datapoints.
My wife and I like to know where the other is because we both do dangerous shit solo. (She horseriding, me motorbiking, and we've both got health conditions). I get notifications when she enters any number of geofences, and can see where she is at any time - and vice versa. This has eased anxiety for both of us.
Initially we used Life360 which is a nice and easy app to use. Then we found out that they sell your information to actively work against you. Not just basic stuff for advertising, but your driving habits, speed, style, accelleration rates - to car insurance companies so they can raise your policy costs, or potentially deny your claim entirely. (Just one reference but there's heaps more)
So we went self-hosted. Traccar is free and I keep our information private. Install a small app on your phone and register it, and done. Or it integrates with dozens of commercial and open source tracking systems.
Disclaimer - not involved with the project, just a user and a fan.
(Just noticed my wife's left her phone behind when she went off riding... I guess no system's perfect!)
DaVinci Resolve is professional grade video editing software that's completely free to use. It lacks some features that the paid version has but this probably doesn't effect the vast majority of casual users.
Right now, it's Calibre because I just got a Kobo eBook reader and it's so great to be able to install pretty much any format of book onto my device and convert it if it's a format the device can't use. And even convert it if the book works better in a different format.
Kodi—It can connect to a media source via FTP, so I was able to effortlessly connected it to my online storage to download shows and movies from it to watch on the fly, and on my TV no less. Without that, it'd be a huge pain just to get the file onto my TV.
SmartTube—It's an ad-free YouTube video app for Android TVs, and it has Sponsorblock included. You could say it's YouTube Vanced for Android TVs.
Discord bots—I've setup my own personal Discord server (no other humans allowed in it) and set it up with various bots that do things ranging from posting tweets/ posts from Twitter/ Bluesky to letting me know when specific channels have uploaded a new video on YouTube or gone live on Twitch. I've also got another bot monitoring some RSS feeds.
Fedora. Switched to Linux full time over a year ago, after years and years and years (like... 06/07?) of dabbling. It blows my mind how polished and wonderful it is to use. It's completely everything I need, and it always blows my mind that it's fucking free
KiCad. It's an electronics design tool on par with commercial options in the industry, which cost a ton of money. Ever since the UI facelift it got a few years ago, it has become my go-to option. They are even working on integrating circuit simulation and finite element analysis, which is just crazy.
VSCode. I don't get why Microsoft hasn't monetized it but I'm glad it is free. Has so many extensions and gets great updates, even if I don't understand half of the stuff in their patch notes when I open up the program.
Another one is a little program called Stacher that basically serves as GUI for yt-dlp. It's a very pretty one though! And all the settings and buttons are super great. I'm not very good with CLI stuff so I'm glad it exists for free, saves so much time.
May be a bit out there, but on Android, Shattered Pixel Dungeon is a rogue lite game that is free and extremely fun to play. No ads, not very demanding on your phone, still gets updates, and easy to pick up and play when you're out traveling.
Its a very hard game, where knowledge is very important, as well as experimentation.
Can nuke your phone's data if not unlocked for X amount if time, along with many other triggers for a wipe.
Very useful considering the political climate of one of the most powerful nations in the world has someone done a nazi salute behind the presidential podium.
Warning: I am not a lawyer. You might get in legle trouble for using this app (Such as "Destruction of Evidence" charges)
Aside from the obvious FOSS offerings, there is a ton of free music software out there, including plugins for your favorite DAW.
While we are at it, Reaper is not free but they are also not going to bug you to pay for it. It is so good and inexpensive that they mostly rely on the honor system for payment.
There are so many complex applications that I can't believe are free: KDenLive, Gimp, Audacity, Firefox, Discord, Calibre, Jellyfin, Rainmeter, Godot, Retroarch
I use cygwin a lot. I fine it extremely convenient. Most of my personal software development is done in gvim and compiled in cygwin. I wven dosome of my professional work, particularly unit testing in it.
I recently learned about an app called Snappy Driver Installer Origin. It's a minimal FOSS program that checks our PC for the drivers it has, needs installed, or updated and goes about it quickly. It's also portable so it's great if you want it on a install thumb drive.
There are so many apps out there that try to get you to buy or pay a subscription for this feature and others, so it's been a breath of fresh air for me to have learned about and use it.
Im going to throw libre office in. Spreadsheets are so versatile. You always here about this is done so badly they are using spreadsheets but that just shows how friggin powerful and versatile they are and the other parts of the suite are nice to.
For work, entire ecosystems of dependencies. For every language, there’s so much you can do by just including a free module.
My company has some decent policies about giving back, but only on a case by case basis. I’ve been encountering resistance from both sides trying to formalize it.
WTF is that developer saying he doesn’t want to scan his opensource projects or take advantage of automated builds and testing, as well as regular dependency updates?
WTF is management so concerned about security and confidentiality but want to just ignore an entire category of components?
We have the tools, we have the process: everyone would be happier of opensource were a first class citizen with well understood rules and practices