My domain is registered with Google Domains, so I did this yesterday:
The app speed did go up, but I was getting the following message just like @eli :
@peterj said it was no big deal, so I happily ignored it:
At that point, I hadn’t tried logging into the app after the changes yet - I just browsed publicly available pages and was happy they were faster.
This morning, I’ve tried logging in and all hell broke loose with invalid login sessions and whatnot. I ended up turning Cloudflare off, disconnecting the new www domain from Bubble, connecting it again as a bare domain, and reverting the Google Domains DNS to the original non-Cloudflare settings. About 30 min later, everything went back to normal and was able to log back in.