The post is about commercial software. If enterprise’s domain is not credible enough, then there are bigger problems.
Well, I too dislikes their enterprise tune, "Changing is consistent, GitHub give you advantage (over other companies)" blahblahblah. Many developers I know are on GitHub because it was/is the place for individual developers to share code, not because the "company advantages".
HOWEVER, I can't ignore the fact that individual developers just can't pay enough to keep the machine running, so it's reasonable for GitHub to pivot towards commercial market. On the other side, GitHub is still benevolent enough to provide some enterprise-class service back to freetier users. This arrangement checks out for me so far.
I do self-host some of my projects too with Gitea. But I never dare to use my domain in my Go packages, due to long-term security concerns.
When I initialize my projects, I just use .internal domain, then if I decided to upload the project to GitHub, I'll change the URL to GitHub to make it more convenient to the users. Otherwise, manual download and `replace` directive like I suggested.