Desktop App freezing when typing + notification

Mh, apparently I was wrong… Now it also freezes after I restarted the application.

Wrong Description of how I thought the application would behave (but apparently doesn't...)

It has been a while, and I’m still suffering from this problem, but I also have a new observation:

The intermittent freezing seems to happen if the Mattermost Desktop client was autostarted during login. If I terminate the desktop client and restart it manually, it seems to work…

I’m using KDE Neon, currently using Plasma 5.18.0, KDE Frameworks 5.67.0, KDE Applications 19.12.2.

Any hints / ideas?