iMessage has lots of problems. I've screwed it up a lot of times switching SIM cards, I can never understand why it needs to know if I want to contact my iMessage contact by email or by phone number, or why the messages thread differently depending on what I use. But it GENERALLY works okay.
Meanwhile, I use Signal with one friend, and just about every time I launch the damn app on my phone or desktop, it complains that I need an update, or I need to re-link something, or my safety numbers of changed, or some such crap.
And it's all better than Messenger.
And all of THAT stuff is better than Google's incessant abandonware. I loved hangouts.. until I didn't.
If you regularly need to relink Signal Desktop, it is likely your disk is failing and corrupting the sqlite DB that Signal Desktop uses. Back up your other data ASAP!
All it needs is research-verified encryption!
Also, Signal didn't quite work in the UAE.