It could be proprietary drivers. BUT I was having some screen tearing a while ago, and I didn’t have transparency. These are my settings if you want to give it a go.
I haven’t tried the LTS Kernal but I have had similar issues when older versions of Manjaro a year ago (before switching to Endevour) and debian buster with kde plasma.
The reason I’m more keen on nvidia being the issue is odley reinstalling the proprietary drivers with nvidia-dkms fixes the issues but the trade off is kwin_x11 starts to use 50-60% of my cpu and animations become choppy until the blur effects are disabled.
I guess filing an upstream bug report may be one option. That said do you know where the source code for nvidia-installer-dkms is? I tried looking on endevour OS’s github but the repo looks archived/deleted https://github.com/endeavouros-team/nvidia-installer-dkms
The high cpu usage and issue fix is the only part that bothers me and that I haven’t seen on manjaro (more cause this wasn’t even an option).