KDE Feedback (the opt-in telemetry) causes the "desktop" to not load or to load to only a flat gray image with the ^ icon at the bottom.
Using PinePhone Pro with Manjaro ARM, with all current packages as of this writing.
After sliding the feedback slider all the way to the right, I experienced the homescreen no longer able to boot correctly after locking the device and then unlocking it. I managed to open the system settings for Maliit from the lock screen, and then from there I navigated back and disabled the feedback feature by sliding it all the way to the left. I was able to repeat this multiple times, demonstrating that the feedback feature is related.
Another user experienced the same issue, and they managed to correct it at least temporarily by flipping the modem dipswitch which allowed the homescreen to load in order to disable it, then re enabled their modem switch.