My main browser is Librewolf but I keep a chromium browser just in case. Previously used brave but their flatpak is shit. Ungoogled chromium seems ok but it looks like they don't change much from upstream chromium. Any good chromium browsers which harden their browsers like librewolf does for more privacy?
What Distro are you on? I use Firefox and Brave, both as RPM now. I actually switched for convenience (keepassxc extension works, plasma extension works etc) but they are actually more secure.
Native Chromium is poorly way more secure than Firefox. When using the Browsers through Flatpak you need to remove the sandbox, so process isolation and memory stuff is gone, and replace the specific sandbox with bubblewrap.
Bubblewrap is good, but doesnt support isolated Tabs.
There are CSS exploits, but to my understanding just using Noscript in "block all by default" mode is best for security AND privacy.
I would like to like Brave, as it is more secure, but it sucks a lot. Very bloated, tab management worse, missing extensions, damn Chromium webstore and the addon not working so no updates. It is not bad, and I want to write a hardening config soon, to remove and disable all that bloat permanently.
I would not recommend Librewolf if you are advanced. For one it is a Flatpak, ironically (didnt know this a few weeks ago too) less secure. Also it lacks behind in updates a bit, not much, but this may become a problem.
I am working on this tool, should work, that keeps your Arkenfox config up to date and sets a few switches to soften it. So you add that to Firefox and dont need Librewolf anymore.
On Fedora all you need is libavcodec-freworld from rpmfusion to get everything working. But ublue.it images work best out of the box.
Edit
Why are you downvoting this? Doesnt it fit your opinion? I also dont like Chromium, but its more secure. I also didnt know that Flatpak browsers are less secure, but thats a fact.
Even though pretty old and probably outdated, some points are for sure true. Some apps like Onionshare are horribly outdated, and unless every app has at least one packager responsible for it, best official and paid, its a total mess.
These where not the sources I refer to, and it is pretty complex. Secureblue disables user namespaces and uses bubblewrap-suid for security, but after madaidans statement that would mean a hole in bubblewrap allows the app root privileges.
Thanks for the additional reading and information. Maybe it's just me, but I feel like I hear about a security vulnerability in "processor microcode" or packages or other software basically every day. As a relatively non-technical user, it's always very difficult to tell how much these things actually matter for normal users. Flatpaks are incredibly convenient because they "just work" and are easily compatible with immutable distributions. For better or worse, I suspect many people are not going to be dissuaded from using them by hypothetical/abstract security risks.
Flatpaks are more and less secure. Their Sandbox improves 99% of apps security as other sandboxes are hard to setup and thus nearly nonexistent.
Browsers have their own, so just dont use Flatpaks there.
I am not sure about microcode, but processes running as root are maybe more critical, but it sounds like any process could have exploits if microcode is a problem. Also, RiscV or even ARM will be waaay better here, as their instruction set is not dozens of years old and extremely bloated.
As we get our apps from secure repos, with projects keeping track of every Git commit etc, we just had no malware really.
The only problem is that Flatpaks, like appimages, "just work" and dont have to evolve like the rest of the OS will. Their main goal is to work everywhere, and Devs always choose convenience over security.
For example Portals are not implemented in most old big projects like Libreoffice, Gimp, Inkscape etc. Scribus is even X11 only. But developers will not remove the filesystem=host permission and replace it with "just all the media locations". This will still be a problem, but at least apps could not read Kernel logs etc anymore.
Also as they "just work" its easy to abandon them and dont update. The "outdated Runtime" Warning is a veeery good indicator of a project using old and probably insecure libraries. But afaik there is no automatic CVE patching in flatpak-builder which is a huge problem.