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 http://fvonline-db.bplaced.net/. I occasionally will back theirs up, and keep it here: https://bluray.beandog.org/keydb/
If you don't want to deal with manually tracking your own keys to rip Blu-rays, I recommend using MakeMKV instead.