playing dvds in debian10

Steps
1. add the contrib (and probably non-free) repo to your sources list
2. install the libdvd-pkg package, and a player
3. run the libdvdcss library installer
4. (might be necessary to) set the region for your dvd device
5. try playing it

From top to bottom
if necessary, change your sources list

$ cat /etc/apt/sources.list
deb http://debian-mirror.sakura.ne.jp/debian/ buster main non-free contrib
deb-src http://debian-mirror.sakura.ne.jp/debian/ buster main non-free contrib

...

(you need to have the contrib repo as above)

if you did any changes, do "sudo apt-get update" to fetch the new repo data.

install the libdvd-pkg

$ sudo apt-get install libdvd-pkg

or better

$ sudo apt-get install libdvd-pkg libdvdcss-dev libdvdcss2 libdvdcss2-dbgsym libdvdnav4 libdvdread4 lsdvd regionset mpv lsdvd

then run the configure script, to compile the libdvdcss library

$ sudo dpkg-reconfigure libdvd-pkg

I don't remember if you needed to do this the first time, or just if your dvd wouldn't play... but try inserting a dvd, and do

$ sudo regionset

Some commercial DVDs won't play unless you have the "correct" dvd region for the region they were supposed to be sold to. Capitalism can be scary.

So, you can select a region, or just leave it as it is.

More info at /usr/share/doc/regionset/README

Finally, let's try playing something

$ mpv dvd://1

And you can check your dvd contents with

$ lsdvd

I'm sure you can also click around with your favorite desktop environment and find a way to play your dvd as well.