I personally wouldn’t go that far tbh, but I haven’t rly looked into it rhat much so idk.
To me it seems like they are still maintaining Firefox, Gecko, and Thunderbird (which is more independent tho IIRC) quite well.
I use Thunderbird directly and Firefox through Librewolf

(haven’t rly had the drive to look into Thunderbird analogues to Librewolf. Should rly do that tho)