I wish I could use it but I can't. The folks developing UT are awesome but they are a very small group of unpaid volunteers and this stuff is painfully difficult to do.
One of the biggest problems is the lack of VoLTE support for making actual phone calls on most phones. Last I looked (which was admittedly more than a month ago) only a few models supported it, and it is the only supported mobile voice protocol in several countries. You can work around this with a SIP (Voice over IP) account and some geekery but it's not ideal.
Another issue is very limited software. There just aren't that many developers creating software for the platform.
I ended up on /e/.