If you launch mullvad from the app icon, try you add to PrefersNonDefaultGPU=true
(or false) in mullvad-vpn.desktop (cp /usr/share/applications/mullvad-vpn.desktop ~/.local/share/applications
If it is autostarted add it in .config/autostart/mullvad-vpn.desktop
Or add --disable-gpu
to the in Exec : Exec="/opt/Mullvad VPN/mullvad-vpn" --disable-gpu %U
Deepin lxQt MATE? Plasma GNOME Cinnamon? Unity XFCE Budgie?
Not sure for the third column