UBports relies on 2014-era Ubuntu-specific software that even Ubuntu moved away from. Consequently, I expect a lot of UBports to bit-rot before its maintainers can make it a reliable and competitive option. Mobian's stack isn't what I would have liked (it is a lot of unoptimized GNOME libs), but at least it seems to have enough corporate backing for development to keep going.
Yeah, both projects have their challenges. It's been good to see them, as well as the Librem developers, working with each other to advance their respective projects where it makes sense.
Just curious, what corporate backing are you referring to? I hadn't heard that before.