[xvdAZh]

Outside of IP-blocking known popular DoH hosts (e.g. https://github.com/jameshas/Public-DoH-Lists, and even then it's not the best since there's overlap with popular DNS hosts like Cloudflare), there's no good way to do it without break-and-inspect. That's because DoH is TLS traffic over 443, just with DNS inside instead of HTTP.