In This link is mentioned that Linux GUI is installed on tty7, but when I change my consoles using Ctrl+Alt+F1-F7 and check it by the command tty, I see that I have a GUI on my tty1 and tty2.
I'd like to know:
Why is in most sources mentioned that the GUI is on tty7?
I have a GUI on my tty1 and tty2 on Ubuntu 20.04, tty3-6 are consoles without GUI and tty7 prints information about /dev/sda2, is tty7 another console? If yes how does it differ from other consoles? If no, what is it?
Which tty's are configured for X11 or Wayland (the GUI) is up to the distribution being used, although a lot follow the '1-6 for getty processes' (which connect a tty to a login process), '7 for GUI' line.
Hardware limitations force some other solutions. I suspect you have one of those. Raspberry Pi?