Here's a good article with some context around the F-droid situation, and why Signal is full of crap.

I think it’s also important to understand that signal is also a company that, at some ooint, needs to make money from somewhere to do this awesome thing and they won’t get that limiting themselves to an obscure app store that maybe 1 in 100 users even know about.

Signal is a non-profit and backed by a billionare. Tbh idk what their financials look like, but they don't seem to be in a difficult funding situation at all.

I also highly doubt that Google would modify the signal binary with a backdoor...

They definitely wouldn't do it for everyone, but if the FBI comes knocking at their door and tells them that they need to access a specific person's Signal chats, deploying a backdoored update to that individual is easily within Google's power. It's extremely likely nobody would notice, unless maybe the target is a security researcher or something. And IMO even if the info does come out, most of the blame/consequences (if any) would fall on the government, not Google.

Considering everyone is being labeled a "terrorist" nowadays by this whackjob administration, this type of scenario seems increasingly likely to me.