Pinephone Plasma Mobile Black Screen after Login Solved

since ive updated my manjaro plasma mobile pinephone on saturday, a graphical login results in a black screen. the screen is still on and holding the power button shows shutdown options, tty and ssh access also still work. the logs said "pam_systemd_home(kde:auth): Not a user managed by systemd-homed: No home for user phalio known". i hadnt heard of systemd-homed before, so i looked it up and tried making a new user with it or migrating my existing user. it didnt help. in fact, it made it worse. maybe i didnt do it right. but i had finally joined public chats (only so far because joining any other channel fails because apparently matrix sux if used for bigger chats, i guess i should finally get into irc) and two days later, the folks there started having the same issue. it seems to be caused by a qt5-wayland update. until the issue is resolved, disabling systemd-boot by using

kwriteconfig5 --file startkderc --group General --key systemdBoot false

fixes it, as per or downgrading to 5.15.2+kde+r41-1.