I think the assumption is that the average Linux user will easily figure out installing DBeaver and PostgreSQL by themselves, plus installation methods will vary depending on distribution. I'm a Linux user and I'd certainly skip that video.
1. There are new Linux users every day
2. The Mac/Windows users will most likely have to install PostgreSQL on a Linux server eventually for production anyway
It would be very beneficial to at least add instructions for installing on a Debian based distribution like Ubuntu, since that would cover the vast majority of Linux users, especially newer users.
At least having the add-apt-repository line in the course manual saves you looking for it on the DBeaver page.
Aside: I've been doing a the Standford machine learning course and it includes installing in the required work, so I did the install on Windows as instructed (what a pallaver) and only then realised it was entirely optional just not presented as such and so then did `sudo apt install octave`, messed around with a few test queries, and was done with the entire second lesson.