Idk how secure telegram is but cmon signal is shady AF . They won't let fdroid have it cause they want to sign their own keys or some shit but there is a speculation its because they can roll out custom apk to targets which governments want which is just not possible if it is hosted by someone like fdroid . Even telegram allows that and they even allow third party apps which signal won't .

SimpleX and briar is the best option if your actually worried about privacy .

This comment is copy pasted from another thread where I had the same opinion