If you install this via flatpak, you shouldn’t have to install anything via apt, the dependencies should be contained in the flatpak runtime. I’d suggest looking for the issue there

What are its advantages compared to the regular one? Genuinely interested

Why use an Arch-based distro if you can’t use the AUR? It’s like one of the most, if not the most defining feature of them

I noticed in the install.sh of GSR, that setcap cap_sys_admin+ep is called on the executable. So if you know any way of replicating something like that for flatpaks that is simpler than installing GSR manually, feel free to let me know.

You can just run the same command on the executable installed by flatpak. On my system it can be found in /var/lib/flatpak/app/{app name}/current/active/files/bin.

dd’ed an ISO onto the system drive instead of a USB stick. Luckily, the first partition was the Windows one, so not too important; and the rest I recovered from the GPT backup table.