I installed Flatpak:
sudo apt update sudo apt -y install flatpak flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo sudo apt -y install gnome-software-plugin-flatpak
Then installed MakeMKV by clicking the Install button here, Software opens and I installed it (source shown was flathub, to confirm I am getting the flatpack version):
But the app does not show up in the Budgie App Menu. I have to launch it via Software.
My only goal is to copy a DVD to a single file that is supported by webbrowsers, without transcoding A/V. MakeMKV seems to get close but only supports MKV, which is not supported by most browsers but I figure I can convert it to a different container like webM or MP4 afterwards.