Yeah they need to get backed up somehow. GitHub probably doesnt offer an API for that
Actually, it looks like they do have an API for that https://raw.githubusercontent.com/github/rest-api-description/main/descriptions-next/ghes-3.6/ghes-3.6.yaml
The repo owner shall file GDPR date export request to backup the issues once a month.
Yeah, issues and comments (which can be quite important for a repository imo) are unfortunately not included in a git repository so migration of these is not trivial.
I will have to look this up. Thanks for your response!