Time Machine is not supported by GitHub Pages

[jeremyzilar]

When trying to build a vanilla Jekyll site through GitHub pages using the Time Machine theme, I get this error:

Page build warning

The page build completed successfully, but returned the following warning for the main branch:

You are attempting to use a Jekyll theme, "time-machine", which is not supported by GitHub Pages. Please visit https://pages.github.com/themes/ for a list of supported themes. If you are using the "theme" configuration variable for something other than a Jekyll theme, we recommend you rename this variable throughout your site. For more information, see https://docs.github.com/github/working-with-github-pages/adding-a-theme-to-your-github-pages-site-using-jekyll.

[DillonB07]

Time Machine is on the supported themes list
But I am having trouble using this theme as well with jekyll. and GH pages.

[devsmagick]

Time Machine is on the supported themes list
But I am having trouble using this theme as well with jekyll. and GH pages.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[MonikaBarget]

I assume that my issue goes in the same direction. When I try to customize the theme, my commits fail because of this error notification:

github-pages 226 | Error:  Invalid CSS after "<": expected "{", was "!DOCTYPE html>" on line 8
      Remote Theme: Cleaning up /tmp/jekyll-remote-theme-20220627-8-1t7h8qg

I really cannot make sense of it.