UBports is not trapped at all. The work with mainstream Linux Kernel is progressing and well advanced.
As they said, specifically for the Librem 5, “Unfortunately, hardware changes between the Librem 5 devkit and the final phone mean that we can’t be certain that any of the fixes we make on the devkit will carry over to the final product.”.
For Pinephone and Raspberry Pi, this problem doesn’t exist. Pine64 sends first to partner projects, each new version of devkits or pinephone according to the improvements made. About Raspberry Pi , the final versions of the devices are available for purchase and very inexpensive.
So the problem of unavailability of the device for UBports is specific to Librem 5 and and this is the main problem for finalizing development.
This has nothing to do with Debian/Ubuntu or GNOME/QT.
Funny to always want to bring everything back to the old, totally sterile wars.