Could gitlab & container registry using same domain?

Can I setup same domain name for both service like
Container registry:

most of guide line is telling us to using different domain name for registry.

Im testing docker login it was success (runner/wsl)
Docker push give 404 error. (Runner)
Docker push give 403 error. (WSL)

I was tried make external_url for registry.
Then both(runner/wsl) docker login fail
Docker login

You can use the same domain (I do too), but you have to specify the port, as you already realized.

Could you please share a bit more about your installation? (How did you install GitLab, full configuration (gitlab.rb), etc) This way community has more chances understanding your configuration and helping you.