Thanks for the fixes, I was able to install plasma 6.1.3 in testing
by enabling unstable and experimental temporarily and doing
sudo apt install -t experimental plasma-desktop konsole dolphin sddm
So far so good.
Note that without updating sddm, I was greeted with black screen after boot due to missing qt 6 based greeter,
so I had to dig into sddm logs to narrow it down. Anyone doing the above, don't miss it.
Regards,
Shmerl.