So I see you clearly haven't heard of i3, sway or hyperland ...
abofim
joined 5 months ago
The Fennec Android browser is currently behind on Firefox security updates, deemed unsafe by F-droid
Mull browser is also available on fdroid. It is an even better (secure) alternative to firefox as it uses some of tor architecture, from what I know.
op forgot to mention that it is a "provisional, read-only manner,” according to founder Brewster Kahle.
Open source? Probably not, but the new instander beta (only available on telegram) is really promising and works well.