I deeply and sincerely apologize if my contribution seemed dismissive. That was by no means my intention. I was not trying to invalidate your report. I was just contributing another data point. Based on this example it seems that the issue might be related to the incompatibility of the current snapshot with some specific system configurations.
The video
You are right, sorry about the misunderstanding: my bad
The version
I did use the snapshot version, not the old one; as per your specifications. I have currently no means to test the AppImage.
The check I reported is using the new version that you linked from the OpenSuse Build Service so I believe we are talking about the same version. Actually, I tested it both on the old vesion I had installed, and then I de-installed it and installed the snapshot you linked to. I could not detect an appreciable difference.
The system
WSL is Linux in a sense. It runs Linux binaries and uses native Linux libraries. WSL is essentially a virtual machine of sorts. I run the Debian, so I installed the Debian package that I downloaded from OBS.
More testing
I am actually planning on having several virtual machines with different configurations ready so that at least I can help testing. Not having a dedicated computer, I will set them up insider a true virtual machine, not WSL (side note: WSL is still useful because it seems to be the only reasonable way to run the guile3 port). I will try to get an Archlinux system running as soon as I have some time.
My experience with slugginess
A similar slugginess you encounter, I encounter it sometimes using the current Release version (not the snapshot) under Windows. However, this may be due to a completely different issue.
I sometimes manage to solved it temporarily by restarting TeXmacs and sometimes by clearing the $HOME\.TeXmacs
directory. Removing $HOME\.TeXmacs\system\*.scm
and $HOME\.TeXmacs\progs\*.scm
has usually no bearing on this so you can avoid removing them and not lose your settings. I think the cache might be the culprit.
Since @jeroen cannot reproduce the issue, did you try clearing the cache?