Just updated to sitely 6 and found a possible but very minor bug.
I noted the php for the contact page submission button now lives on it’s own in the root and now the page becomes thank-you.html. No problem there all works fine.
I like to use clean url’s so i did the site/folder/index.html thing. It again works but you literally see site/folder/index.html with the index.html in the address bar. I tried creating a new page which worked fine so I’m guessing it has something to do with the thank-you page selection under the hood.
Doesn’t affect functionality tho.