!Friendica Support sorry, this post here:

https://friendica.ironbug.org/display/3217dd65-795f-e050-adca-72b996613149?owt=ecd65c98e5835f552556a4809c5d0d84

it wasn't Friendica, it was mastodon. but really does not matter. I suspect the whole REST API would fail with Cloudflare stupid filtering.

just I stomped on it. if you need an example it was noagendasocial.com. I don't know. maybe there're more Fediverse servers there with the same problems.

I don't know about the Cloudflare, if they filter everything or just 443 port. maybe REST API and json could work on other ports, not sure. never used it.
but one more problem with Friendica (and ActivityPub as a whole) is mixing HTML and json output on one port. this, for example, creates a serious problems with caching of pages. because user without session and server are indistinguishable for HTTP server and cashe becomes pain in the butt. after a lot of experiments I seem found a way to make cache work on Nginx at least in most cases. but this was quite unnatural solution.
I think, ActivityPub is still a raw draft. not a ready to use standard yet.

I think we barely can do anything with Cloudflare requirements.
if instead of server info json it gets an HTML response with asking to turn on JS it must be excluded from the list of servers for profiles explore.