I am having this issue with a brand new install of WordPress, and it’s the only site of the 20 or so I maintain that is running 5.7. Other sites using prior versions of WP are not experiencing this issue.
On the problem site, https://topknotchcabo.com/, no plugins are active, and the active theme is Twenty Twenty-One. After installing WP, I added a blank page and a blank post just to make sure everything is kosher. Got a redirect error.
Deleted cookies and cleared browsing history. Redirect still there.
Deleted the database, deleted WordPress, and reinstalled the whole ball o’ wax. Still getting the re-direct loop.
Any other ideas?