F-Droid
F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.
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I don't have an answer to your question, but if it might help- I recently learned about an app called obtainium that apparently makes it a lot more practical to install apps directly from github, gitlab, etc. and keep them updated.
I hope you find a solution that works for your needs!
Mulch, it is available on an fdroid repo from divestOS. Mull can also isolate pages
Sadly seems like it, and either way I don't think a security critical app like a browser going ghost mode for so long is acceptable. If you're using Play or the Aurora store, brave is an option otherwise its only Graphene and Vanadium I'm aware of.