Sitemap with relative URLs and Google Search Console

Hi there,

First of all, thank you for this great theme that I am currently using for my site on github pages.

I have a problem with the sitemap generation to allow google to index the posts I am adding. By looking at the sitemap, it looks like I'm correctly generating everything with absolute path as required by Google. However, when I tell Google Search Console to scan my sitemap, it generates this error:

The error says: "sitemap index can be read, but has errors". It looks like in the examples that the URLs are missing the domain and subdomain, but I can't understand where in the source code I should include that (url and baseurl are correctly set in my _config.yml).

Thanks for your help!