likely the ISP would block them too

"ISPs blocking ports" is such garbage, because the whole point of internet access is to provide access from point A to point B, which the customer pays for. I imagine the ISP wants to block ports to sell their own media services or something anti-competitive like that.

Anyway, you have Enet sources, so putting an additional field in the header of 32 bits or so called "forward_to" would be simple. You can then build a simple Enet proxy that knows how to receive this packet, look at the field, look up the value in some forwarding table, and forward to your own servers.

Nothing like using layer 7 to work around a broken layer 3 :-)

I doubt so. I think it might be more of protection on 4G network. Anyway some providers works, some don't.

I have more than just Enet so potentially there's a bit more work to do so hoping for existing solution. Also the proxy would be the bottleneck so it looks to me like LVS Direct Routing is still the way to go.

Thanks for the replies so far.