I'm daily driving a Librem 5 with postmarketOS quite comfortably without any major issues - the experience is light years ahead of the default OS PureOS Byzantium. With the Liberty Phone, it should be even better due to the increased memory and storage which would make it easier to run Android apps using #Waydroid.

Have you seen Flx1 from Furi Labs? It has even better specs, is closer to #GNULinux compared to Ubuntu Touch, and comes with #Flathub and Android app compatibility set up out of the box.