If accessing a Blu-ray disc with DRM, you will need a KEYDB.cfg file in ~/.config/aacs/ to bypass the encryption. You can download a key file or create your own using FindVUK on Windows.

Best place to download one is from I occasionally will back theirs up, and keep it here:

If you don't want to deal with manually tracking your own keys to rip Blu-rays, I recommend using MakeMKV instead.