Well, Wikipedia: en.wikipedia.org/wiki/DVD_region_code#Computer_DV…

Basically same as regions on standalone DVD players. Just a scummy thing to only allow you to play DVDs from your own region, perhaps so that you wouldn’t buy them from cheaper countries, or buy them earlier you’re supposed to in your country.

If everything works correctly, then say you buy DVDs from UK, but something new just released in US, but haven’t even played in cinemas in UK yet. So you buy it from US… and it shouldn’t work.

VLC doesn’t care about this, but still, the drive firmware might.

BluRays also have regions

By the fucking way, BluRays have some DRM with revocable keys

This is part of the AACS protection scheme: editors are able to revoke old software player host keys that have leaked on the Internet and distribute the lists on newer commercial disc releases. This is irreversible and cannot be fixed even after reflashing the drive.

wiki.archlinux.org/title/Blu-ray#Revoked_Host_key…

So when do you truly own something? When you pirate it. No regions, no DRM, 4k on any device powerful enough.