It's up to them at this moment! Kiwi wasn't supported from some time either.
Maybe Firefox... one day... ;)
Some disconcerting info about kiwi browser privacy
nostr:npub1getal6ykt05fsz5nqu4uld09nfj3y3qxmv8crys4aeut53unfvlqr80nfm wen mull browser support?
Discussion
So you don't have a roadmap for Firefox? Since that has extension support on mobile (android, at least), it would probably garner a decent number of more users. Mull and Fennec are derivatives of Firefox (so are Tor Browser and the new Mullvad browser) so it could pick a decent number of users