LineageOS for MicroG: the ROM on my second phone where I quarantine my use of apps that refuse to work without Google services (mostly stuff I need for business travel e.g. Amtrak, Google Maps)
Aurora Store: allows installation of most Play Store apps without login. I mainly use this on the MicroG phone, but it's also needed to get the ProtonMail and ProtonCalendar apps (only ProtonVPN is on F-Droid)
TrackerControl: allows fine tuned domain blocking on a per-app basis. Often allows you to block just ads and trackers but still be able to use an app or at least many of its features.
Arcticons: monochrome line art icons (because I hate fun and want my GUIs to look like a terminal)
AsteroidOS Sync: WearOS replacement. AsteroidOS still has a long way to go, but I doubt WearOS would play nicely with LineageOS and I don't want all the tracking anyway.
Bubble: bubble level by woheller69 (a true F-Droid GOAT)
FlorisBoard: afaik, only FOSS gesture typing Android keyboard (besides AnySoft, which doesn't seem to work consistently)
GMaps WV: fairly locked-down web viewer for Google Maps (sadly OSM just doesn't have a usably complete business directory where I live)
Lawnchair: launcher with all the features I want except being up to date on F-Droid
Librera: the PDF reader on F-Droid that I hate the least. (Anyone got any better recommendations?)
Signal: because I can't convince my friends to switch to Briar
SpoTube: pirate ad-free Spotify that works by looking up tracks on Youtube. Is therefore limited by what's available on YT and sometimes plays wrong tracks, but you can't beat the price :] Even interfaces with a Spotify account to play and edit playlists.
Standard Notes: E2E encrypted cloud-synced notes. Also accessible by web browser, which has saved my ass a few times while phoneless
FairEmail is a great email client. Also everytime I reinstall my phone, I get the SimpleMobileTools line of apps, their apps like gallery or calendar are nice-looking and useful.
Blender and Firefox for me have always been the apps that have their shit together the most. Both I perceive as insanely complicated pieces of software with a lot of features that work really well and compete with for profit corporations with way more resources.
-Tachiyomi for manga
-personal Dns filter for blocking ads system wide
-Aegis for two factor authentication
-NewPipe x Sponsorblock for youtube
-Fritter for Twitter without an account
-Librera for reading my ebooks
-Feeder for RSS
-Quillpad for a Google Keep like local alternative
OpenVPN. I can self-host a lot of different things for my own personal internet/cloud thingy - Bitwarden, Pi-Hole, etc; but to actually use it when I'm not home? I either pay for a VPS or I just have a VPN back to my home network. So much becomes possible with that; like I have the contents of my entire NAS at my fingertips even if I'm not home; I can render projects on a VM at home and manage it from my phone, etc.
OpenVPN is, without a doubt, the most important part of my infrastructure.
Calibre-Ebooks managment
Libre Office- instead of MS Office
Bitwarden- password manager
Mozilla Firefox- browser
IceCube, Pixefed app and Mlem for Fediverse
Joplin- notes
BookPlayer app for Audiobooks
Nextcloud for storage
For me it's ViMusic. I was stuck with a shitty Spotify subscription that I couldn't afford until I found Vi. It has pretty much all the bands I like and it passed my moms rigerous examination (she listens to all of of really obscure stuff) so when her Amazon subscription ran out, I got her to start using that instead. Suck it jezzy b!
KDE Connect means that I can ping my phone that's usually presumably somewhere behind my bed or on a counter somewhere, without having to sheepishly walk to the nearest person and ask "can you call my phone I lost it :c"
Osmand - I use this along Google maps, but it's nice to have entire regions downloaded and it shows more information than Google maps, specifically for back country stuff where you need to see every type of trail
Home Assistant
Wireguard - I love that the protocol is lightweight and secure, makes it really easy to access my home network without needing to expose self hosted stuff to the internet
Bitwarden - self hosted with vaultwarden/SQLite, changed my life and it's really easy to share logins with my partner
Immich - self hosted, the first real replacement for Google photos I've found. It has autobackup and it's really easy to share albums.
Kiss Launcher - I like how simple it is. My home screen ends up disorganized anyway so it's honestly just faster to have a recents list and a quick search feature.