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

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.