I haven't ever noticed Cloudflare having any issues on Firefox, so presumably that implies any unilateral actions in web standards have been worked around by CF to provide the service to Firefox as well.

I'm pretty frequently blocked by Cloudflare when I use Firefox on OpenBSD -- apparently it's too suspicious of a combination for their liking, or something. Even on Linux I've occasionally had issues. I've had to email site operators to ask them to change their configuration so I can actually be a customer of their business.

Oh dear. That is tricky. It must be a rare enough combination that it looks like automation.