More recently they've started collected the contents of messages into the cloud too, yet to this very day their privacy policy opens with the lie: "Signal is designed to never collect or store any sensitive information." which hasn't been true for a very very long time. I consider their refusal to update their privacy policy to be a massive dead canary warning people that the service has already been compromised, but feel free to take your chances.
I'm also not sure where you've read that they collect the contents of messages, because as far as I'm aware they still aren't doing that and I can't find any info online that indicates that they are (other than their secure backup feature that's opt-in only I suppose)
The fact that Signal users are still unaware of where their data is going and when should tell you all you need to know about how trustworthy the service is. Not being 100% clear about the risks people take when using software which is promoted for use by people whose freedom and/or lives depend on it being secure is a very bad look for Signal.
As for message backups they are at least opt-in (for now anyway) and you can learn more about them here: https://signal.org/blog/introducing-secure-backups/
Alternatives?
Was hard enough getting my circle on signal.
You do realize that Signal's CEO is a "former" CIA asset, don't you /s
