I don’t normally see that welcome screen, because I uncheck that box for “Show next time”. This time, I first used CTRL-ALT-F1 to get a terminal login. I logged in there, and went to “.config/autostart” and removed the “.desktop” file that blocks it from showing.
I then logged into KDE, and got pretty much the screen that you are showing as the “Old Welcome”. The message on the bottom line was different, but otherwise it was the same.
But when i start it from the menu i can see the green screen (what you called “The current Welcome after update …”) for one or two seconds and then the “normal” Welcome screen (what you called “Old Welcome”) is displayed. So probably you just have to wait a bit longer or check the journal for any errors.
My system:
Operating System: openSUSE Tumbleweed 20210904
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.85.0
Qt Version: 5.15.2
Kernel Version: 5.14.0-1-default (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-7820HK CPU @ 2.90GHz
Memory: 62.6 GiB of RAM
Graphics Processor: Mesa Intel® HD Graphics 630