Cannot open virtual console 7 (Permission Denied) when trying to start X on Gentoo

startx works fine on my system (Fedora). However, one outdated page on the Gentoo Wiki mentions a different way to run it:

startx /usr/bin/i3 -- vt1

1 is the number of the "terminal" you are logged in on. If you are not on terminal 1, then adjust the command accordingly.

Apparently this fixed the Permission denied error, and allowed X to start.

I don't understand why startx would need this to be passed explicitly. I don't understand how Gentoo could be doing anything differently to Fedora here. Oh well. At least it should stop startx / Xorg from trying to open tty7. That was definitely not the modern way to do things, and it was not working for you.