I’ve been buying physical media and want to save digital copies for SD card. I had no issues with my CD for music but DVDs don’t work.
I have an optical drive that I plug in and it works. VLC with libdvdcss installed through Discovery failed. I tried MakeMKV but it doesn’t detect the optical drive.
Flatpaks are often restricted on what resources they can access because of how they work. I am not sure of the exact option you will need; but my guess is under devices, you can allow USB devices, and specific folder paths and it may work.