What is a reasonable set of ports to block on a WiFi network?

I sell software on an appliance that relies on Zerotier for remote administration, monitoring, updates etc.

Zerotier is a VPN that uses STUN / WebRTC-like techniques to establish P2P connections behind NAT. It makes outgoing UDP sessions to multiple IPs on random ports

It's typically deployed at small businesses where it's wired to the ISP-issued router.

However, one of the deployments at a large corporate network went offline after they filtered everything but 80 and 443. How do I convince them it's a bad idea?