Then don't put it on 443 and pretend (badly) that it's TLS 1.2. Given that QUIC also uses 443 (and 80) without too many problems and that doesn't look anything remotely like TLS, presumably non-TLS 1.2 traffic to 443 is OK.
The problem isn't really the port used, it's the uncanny-valley approach they took in creating something that looks like a creepy zombie version of TLS 1.2, which keep-suspicious-things-out appliances quite rightly get suspicious over.