You can (at least temporarily, until the app's next update, then you might have to do this again) solve this by adding
--force-device-scale-factor=2 as a command line parameter.
This can be done by editing the specific app's (e.g. KeepassXC) .desktop file.
To find and edit it, follow those steps in a terminal (ctrl + alt + t):
List the files to find the desktop file to edit:
Open gedit as admin (
sudo can't open graphical apps on Wayland. If you're on X, you can also use
sudo instead of the
admin:// protocol), for example:
Exec= line, add
Exec=env BAMF_DESKTOP_FILE_HINT=/var/lib/snapd/desktop/applications/spotify_spotify.desktop /snap/bin/spotify --force-device-scale-factor=2 %U