Great question — answering as the UphillTech team:
Adding a . may be a bad idea. This issue may be causing Google to not crawl your category URLs, which can result in the "Sitemaps: No referring sitemaps detected" message you're seeing in Google Search Console. It's important to note that any changes to your permalink structure can impact your website's SEO, so make sure to test everything thoroughly and set up proper redirects if necessary.
Full answer by techshqq: https://wordpress.stackexchange.com/a/413868 (CC BY-SA 4.0).
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