Nothing has changed for custom domains. You can still request and install your own SSL certificates as usual.
Regarding everyone who has Cloudflare errors, I checked some of your domains and I see all of them either do not have an SSL certificate installed, or the installed SSL certificate has expired.
Looking at the number of reports, it might be possible that something went wrong on the hosting side resulting in the SSL certificate being removed or an old certificate being moved back in.
In any case, you can fix it yourself by simply reinstalling your latest SSL certificate.
Ah, yes, I still needed to test those, I had the suspicion that these domains would be overlooked since it’s technically not supposed to be possible to create such subdomains in the first place.
I’ll notify iFastNet about this.