I am speculating if this could be some wayland related interaction.
I mean - only a few days ago another member @Edward78 had a similar issue on Plasma.
The member is known to do a lot of customising - I don’t know what came of it - I initially thought it was a new customisation conflict - but when your topic came up - I thought of the resemblance.
I decided to spin up a vm (4GB RAM, 4cpu and 32 GB diks) - during installation I hovered the icons - and saw zen browser - thinking - hmm - how do that look.
I totally slowed the system to a crawl after the first introduction screens.
Switching to a TTY - took more than 10s to switch - pulling up htop - filter on zen - the htop was filled with zen processes - no wonder it crawled - I decided to reset the vm and purge the disk for another try.
That may just be me - expectation et.al. - I have the community Cinnamon spin (team maintainer) on 24G disk with 4G ram and 2vcpu - it runs quite differently.
Perhaps it has something to do with Wayland?