My site is located at michelle.dev/d8b7. When I save a node, it ends up in the xmlsitemap loc field like "/d8b6/node/12" which causes the sitemap to have http://michelle.dev/d8b7/d8b7/node/12.
I don't have a patch ready for this, yet. Just noting it as it's the next issue I'll tackle and I'm stopping for the night.