Hi,
Recentely I managed to get the nvidia gtx 1650 graphics card on my laptop activated. Mostly it seems to work but there is one especially annoying thing. Whenever there is a system notification something crashes and plasmashell starts using 100% of memory. At the same time the panels stop to be responsive so I cannot use them to start or switch applications. The problem can be temporarily solved by restarting plasmashell in a terminal window. This helps until the system spits out a new notification. So, in the system settings, I disabled all popup notifications but there seem to be some which cannot be disabled.

Would there be a way to either solve the problem by blocking ALL popup system notifications, or change the configuration so that a popup does not crash the system anymore.

I'm running the most recent kde5 on an up-to-date debian buster system. The nvidia driver is version 460.39.

All help highly appreciated.

Which exact Plasma version? Please use the System Information in the System Settings or KInfoCenter directly, there is an option to copy this information to the clipboard.
It is not really useful to give the distribution version only, with the amount of different distributions and Plasma versions out there this doesn't help.