Something's wrong with gdm (black screen on boot)

Q&A
1

Greetings. After installation and some usage I discovered strange things happening with gdm.
After boot, gdm won’t start automatically, I have to switch another tty and execute sudo systemctl restart gdm sometimes twice to make it work

System installed on Intel Core i5 8250U, no additional drivers installed.
I also have AppIndicator extension for GNOME

2

You’ll have to dig into system logs (sudo journalctl) and see what is going wrong. I assume that gdm.service is enabled?

3

Checked journalctl.
I found a lot of gnome-shell[979]: failed to bind to /tmp/.X11-unix/(increasing number): no such file or directory lines.

So I checked permissions of / and it was set to my user for some reason.
chown root:root / solved the problem