I have Linux installed on its own SSD, and project files on a separate HDD which is shared by Windows. This other drive is read-write mounted, but I can’t even access the /media folder to find it when importing. Is that normal?
My guess is that it is related to using flatpak/ flathub. I am not familiar with flatpack, but most containerized apps have permission issues. That may be causing you not to see the mounted drives.
The official binary download from the ardour.org website will likely work fine.
I expect flatpak is the issue.
flatpak sandboxes applications and prevents them from accessing system resources.
There is nothing we can do here, we (Ardour devs) recommend against using the flakpak version, which also has issue with system-wide installed plugins and 3rd party plugins.
I suggest you contact flathub packagers about the issue.
FWIW, given the choice on a system dedicated to recording / mixing audio (or sampled MIDI instruments), I would prioritize having the media on an SSD, over having the O/S on an SSD: optimizing reads from / writes to the media drive will likely make your Ardour experience happier.