Wireguard only supports UDP. The main reason being TCP over TCP is extremely slow.

You could try OpenVPN, I think that has a TCP mode though, as said, don't expect good performance.

For my setup, I used UDP port 443. For the vast majority of situations it works well as TCP 443 is for secure internet traffic. It seems admins often blanket 443 port open regardless of protocol 🙃

Good news: it's possible! :) From Known Limitations on the Wireguard project site:

TCP Mode

WireGuard explicitly does not support tunneling over TCP, due to the classically terrible network performance of tunneling TCP-over-TCP. Rather, transforming WireGuard's UDP packets into TCP is the job of an upper layer of obfuscation (see previous point), and can be accomplished by projects like udptunnel and udp2raw.

Have a look into udptunnel and udp2raw and see how that works in your environment.

As long as you're certain your wireguard server works from other networks.. You could use nginx as a proxy to have your server accept incoming traffic from UDP port 53 (DNS)... But, be careful!

I would strongly suggest you whitelist the retrictive network for use on UDP port 53. Is the WAN IP static on the restrictive network? Do you know the size of the WAN subnet? I'd try a quick test over UDP port 53 using nginx, then close it up. If it works, create your firewall rule to whitelist only the restrictive network and Bob's your aunt.

Try UDP port 123 sometimes that goes through the firewalls