But if you're a cheapskate like me, you need to block by IP address! The links below have a list of Fortnite (~750) & Twitch (~150) IPs, discovered as my kid plays the game. The IPs are kept fresh by verifying TLS certificates.
These can be used for a blocklist, of course. But I've found that policing traffic down to 16-64 Kbps makes the game totally unplayable, but lets my kid use his autoclicker (which I'm told is important to earn experience or vbucks or something. sigh...)