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Apologies for the delay! I believe Port bridge or Reverse proxy of Relay HybridConnections feature
would help your scenario.

To highlight more, HCM is point to point and a feature found as part of App Services.
Each HCM can support multiple Hybrid Connections. Also, any given Hybrid Connection can be supported by multiple HCMs. The default behavior is to route traffic across the configured HCMs for any given endpoint. If you want high availability on your Hybrid Connections from your network, run multiple HCMs on separate machines. The load distribution algorithm used by the Relay service to distribute traffic to the HCMs is random assignment. As I understand your scenario/requirement is for two different networks. Natively, Azure App service does not support this.

Kindly take a look at these docs of Azure Relay HybridConnection SDK samples- https://github.com/Azure/azure-relay/tree/master/samples/hybrid-connections/dotnet/portbridge for relaying TCP Duplex style communication (which supports arbitrary binary protocols).

Port Bridge is a point-to-point tunneling utility that allows mapping TCP listener ports and named pipes from some machine on network A to another machine on a different network B, and make it appear as if the listener were local on network B. For relaying TCP Duplex style communication (supports arbitrary binary protocols).

If only HTTPS support is needed this may work for your scenario. It's simpler and doesn't require an ‘agent’ running on the sender side of the communication:
https://github.com/Azure/azure-relay/tree/master/samples/hybrid-connections/dotnet/hcreverseproxy