Hi,
Updating to 5.4.5 and Google-Sitemap 2.3.3 we're experiencing missing ContentType on Google XML Sitemap requests again.
I think this is related to the Content-Type-Handling changes implemented recently (causing lot's of troubles btw.), see the linked epic.

This has been previously reported with MGNLGS-113 and has been closed as duplicate, although I can't figure out why..

Anyway, this time the issue is reproducible on demo author, see screenshot or:
1. on demo author: create a google sitemap "travel"
2. access the sitemap using https://demoauthor.magnolia-cms.com/sitemaps/travel.xml

The response content type is text/html whereas it should be text/xml or application/xml. It might be that Magnolia itself doesn't set the content type at all but the Apache HTTPd in front does so (this is the case with our and probably your demo installation).

This bug is probably a regression bug introduced with MAGNOLIA-6452