I don’t use gvim (prefer vim myself) but I’m pretty sure anyone looking at your post will want to know more about your graphical sub-systems…
ie.
Your Desktop
Your gpu
Whether you’re running the default driver or anything you may have specially configured.
Perhaps whether you’re running Wayland.
In the meantime you can of course experiment based on what I suggest you posted… for instance
If you’re running KDE/Plasma, you can easily switch from Wayland to xorg by disabling auto-login and selecting the appropriate Desktop when you login.
And, do you see the same behavior in any other similar apps, eg if you’re running KDE you should also have Kwrite installed.