Sorry that I'm answering just now. Thanks for your response but I quickly disposed of any evidence that pointed towards me trying Gentoo, so I don't have any errors anymore.

The issues occurred after executing this command:
emerge --ask --update --deep --newuse @world
which is right after chrooting into the installation. I think it failed at some qt stuff.
I watched some other people installing gentoo and they never even ran that command (at least up to the point I watched them) so I tried doing it that way and it failed again. It's quite upsetting that even when following the guide closely and using a virtual environment it's still so easy to run into issues.

I might get back to you though if I give this another shot.