I just did this on a website that said my Simplelogin alias isn’t allowed for signup, but changed it successfully after the fact from a disposable email.
I just have my own domain (and mail server). If you don’t want to host a mail server (and you shouldn’t), you can get a mail forwarding service to forward all *@domain.tld emails to your email
I got GitHub destroying 2 accounts of mine after doing something very similar. First try I thought it was a mistake. Second time i realised I was actually getting caught by some internal AI.
Could you appeal it and offer to change the email to a non-banned domain? Because that’s quite severe, your GH account has all your repos, issues, and repo forum posts.
I tried, they answered something along the lines of “this account is unrecoverable due to guidelines blablabla”. I had nothing, maybe a couple of issues in some repos, nothing illegal at all.
I bought a domain for $15/year that I use in these cases. It has the added benefit of being able to manage it through the simplelogin dashboard.
I do the same but it doesn’t always work. I forget which site it was but there was one I ran into that checked the dns records. It blocked any domain that points to simple login servers.
Sadly privacy is inconvenient. That’s the world we live in.