I use a LineageOS phone as my daily-driver but I still keep my UT phone when I found out another major update occurs. I believe UT will get much better in the future.
One last thing, aside from issues with Signal on UT, were you able to install any non-openstore apps?
I just read a post on UBports with instructions of how to install Android apps from Waydroid and desktop apps from the stock app Libertine. In order for apk apps to work, I've read F-Droid works and so should Aurora (front end for google play store apps) if you need to install more apps. You could download Signal from Aurora and see if it works.