There’s no cloud services in Jellyfin. You have to set up a VPN on your server, and an account for them on the VPN, plus create a user account for them on Jellyfin. It’s not impossible, but it’s more work.
Since it cleared up on its own, it was probably that.
Another cause could be that you have some malware on your network that is attacking sites.
The author could be infected with something that wakes up sporadically (perhaps on external command) to participate in an attack, and then returns to dormancy. So the Cloudfare block being lifted isn't necessarily evidence that all is well.
(Author here.) This is possible, but implausible. I log network traffic and haven’t noticed anything out of the ordinary. The point of the article was mostly to complain about the lack of information from Cloudflare, though. I don’t know what caused the blockade, and they’re not telling. How am I — as an end-user — supposed to do anything about the situation? I don’t even know what the situation is.