No desktop after 2gb pacman update

hello Manjaro community,
after a major update manjaro does not start kde anymore. with alt+ctrl+f2 i can get a command line, but sofar that didnt help
startx gives a fatal server error (EE) no screens found
kdeinit5 results in aborting $DISPLAY is not set
Please help, this seems beyond my capabilities and the machine is actually the heart of a community radio that would sourly miss it tomorrow.

Assuming you still have internet connection, run

inxi -Fazy | curl -F 'clbin=<-'

and post the link.

thank you very much for your answer! if i try that cmd line at the $prompt i get a > prompt. repeating the cmd there results in: curl: no url specified!
strangely (for me) i also cant use the live-usbstick i had thought might be useful: i can choose it in grub but then that gives me an error that it didnt come online within 30 seconds.

maybe this helps in analyzing: sudo pacman -Syu results in synchr. package databases, core, extra, community, multilib are up to date. starting full system upgrade, then Warning: deepin-desktop-base: local (3:2019.07.10.1) is newer than community (2:2020.11.04-1) and warning: deepin-wallpaper: local (2:1.7.7-1) is newer than community (1:1.7.7-2)
there is nothing to do

Well first off that means your packages are out of sync with the repos.

sudo pacman-mirrors -f && sudo pacman -Syyuu

But also … those arent KDE things … those are Deepin things … why do you have them?

PS. Please also see this: How to provide good information

thank you and sorry about the format - i am troubleshooting from the phone and cant copy the inxi -Fazy results or error messages.
i ran the synchronyzing command you gave and really am not sure where those deepin packages come from.

ah, it must have come with the deepin boot maker - we did use that from deepin org and i guess we shouldnt have

here the exact error msg i get when trying to boot from the usbstick i used for the installation:

/dev/disk/by-label/MANJARO_KDE_2003 device did not show up after 30 seconds
Falling back to interactive prompt. You can try to fix the problem manually, log out when you are finished.
sh: can’t access ttt: job control turned off

hello dear Manjaro experts,
still trying to get back to booting into kde desktop.

was missing the ‘plasma.desktop’ entry in the ‘Session=’ line

i fixed that as suggested in Black screen since the latest update (tty ok)
but unfortunately the system still wont boot into kde.

my suspicion is that deepin-bootmaker is somehow responsible. does anyone have a suggestion how to continue? merci!