Buddy had one. Second-hand, it seemed like a tremendous pain in the ass, didn’t allow him to do most things, and in the end it seemed a moot point. The radios are all closed source/proprietary, it connects to closed source/proprietary/corporate-controlled towers, and you’re sending data to people running totally insecure devices. Ultimately his use case was to just establish a VPN connection to his home computer and route everything through that.
I can see getting into a Linux phone for the interest of the operating system and trying to push the technology, but if it’s a security/privacy issue, I think you’re much better off either using a dumbphone or a burner.
Sony made some significant changes between the PS4 and PS5 controllers. I don’t know the details beyond the dynamic resistance triggers, but if you buy a controller board to make your own fightstick, it’ll work with everything up through PS4 and then you need an additional daughter-board to make it work with the PS5.