All my applications scale perfectly fine (in that they just don't change their scale factor when moving from monitor to monitor). But somehow lmms scales very weirdly. The main monitor shows the program way too large (like in the photo, that is fullscreen) and my side monitor shows the application in slightly too small scale and the text is miniscule. This video shows the difference between the two: https://youtu.be/r8IIEwjYbEo Does someone know what might be going on here? I'm running Debian 12 with Gnome 43 (seemingly X11) with the website version of lmms (stable)
Debian is LTS in your traditional sense, so it doesn't have the full Mutter feature set that current GNOME has. So X11 is probably your best bet if you're running Debian 12.
Also, judging by this article article Wayland is on by default.
A way to check this is to find the About pane on the GNOME Settings window to see if it's running under X11 or Wayland.