This exact issue years ago made me think less of (and stop using) Signal rather than F-Droid. You're better off with XMPP or Matrix, plus an ordinary SMS app.
Stellar UX are always welcomed, But the network effects of a chat application are too high of a variable for to just rely on stellar UX to be successful.
Case in point: There was a chat app called Hike[1] in India run by the son of the leading Telecom Billionaire. It had more features(free SMS, Stickers) and arguably better UX than WhatsApp according to its users(100M). But it could never gain over WhatsApp's initial market size in India(Why change what works?).
Final nail on the coffin for Hike was when WhatsApp was made available on the 4G feature phone released by a competing Telecom operator and loads of people got to experience WhatsApp on their first ever Internet enabled compute device.
Yeah or any kind of cartel, really. It's hard enough for a small coop to fight economies of scale, but in many areas you're facing an actual mafia.
Somewhat off-topic, but what's the situation with DIY non-profit ISPs in India? If you're not familiar with the topic, you can look up NYCMesh (New York), Guifi (Spain), Freifunk (Germany), FFDN Federation (France) or Rhizomatica (Mexico). Another interesting development in the telecoms field is https://jmp.chat/ promoting and developing free-software for cellphone<->XMPP/SIP interoperability.
You may be interested to learn that stellar UX is an important point for the snikket.org family of XMPP clients, despite not being there yet. There's an upcoming UX study if you'd like to take part: https://snikket.org/blog/simply-secure-collaboration/
Only reason someone is able to do that now is because WhatsApp, Messenger gets into some legal trouble and the media advertises Signal.
Preaching about significance of interoperable protocol and suggesting apps which use them is beyond the capacity of even those media.