My Chrome has no problem staying on the http version
Neither did mine until a few days ago

It automatically reverts to HTTPS whatever I do. Is OK in Incognito though if I remove the s.
Query of aurora2.pentarch.org in Chrome Domain Security Policy page for HSTS/PKP returns a list of policies including ...
"dynamic_upgrade_mode: FORCE_HTTPS"
Delete function does not work, meaning it is preloaded.
So if admins want to do something about that it looks like you can remove a domain from the preloading list. Scroll down for the removal form link.
https://hstspreload.org/