Definitely Signal. It strikes the fairest balance between industry-standard end-to-end encryption ('E2EE') and usability.
Get as many of your contacts onto Signal as you can. Disable the displaying of message text within device notifications from within the Signal app settings (for both Android and iOS).
GPG doesn't support forward secrecy, which is table stakes for encrypted messaging these days. And that's to say nothing about the slightly suboptimal usabilty...
True, but you're not trusting any corporation to do what they say they are doing, or not changing it out from under you. I guess you're trusting the Gnu people though.
Signal and Threema seem to be known for good UX and viability as everyday messengers.
There was this table: https://www.messenger-matrix.de/messenger-matrix-en.html