On Linux I've tried/used the following browsers to replace Firefox:
- Zen (Firefox)
- Floorp (Firefox)
- Librewolf (Firefox)
- Vivaldi (chromium)
For the last several months I've been using Floorp and am happy with it. I use Librewolf for accessing Meta.
On Android I've used Firefox for day to day and Waterfox for accessing Meta.
IANAL: my concern is how much of the new Mozilla TOS is directly applicable to Firefox forks.
The new TOS reads like Mozilla is legally allowed to 'tee' anything you upload to their own information horde, including anything binary.
Also, something I've noticed is that sometimes when Mozilla upstream makes TOS/marketing/affiliate changes via about:config changes those changes get pushed downstream and if the downstream team misses it in the rush to get the new version out the door you may end up with these settings re-enabled.
I tried Vivaldi yesterday. Ad blocking isn't sufficient to use it as a daily driver browser. Unusable for me.
Eyes to the future for open source browser engines.