How to create a subdomain for a site on GitHub Pages?

Question

GitHub

There is a domain with DNS from Mail.ru Mail for the domain.
There is a site on GitHub Pages.
The domain is linked to GitHub Pages (2 records in DNS, CNAME file in the root of the project). How can I create a subdomain for a site (like subdomain.example.github.io) so that when opened it opens at subdomain.mydomain.com?

Answer 1

This must be supported by the host site.
Those. with GitHub Pages - this will not work.

Answer 2

Probably create separate sites on GitHub Pages (example1.github.io, example2.github.io) and link subdomains of the same domain to them.