@OldSurferDude well, the ESP8266 is limited to 4 TCP clients in arduino IDE. This can't be really increased. I did som experiments and you can set it up to 15, but after the 5th client on my web server, I got a freeze.
Maybe you got something wrong. #define MY_GATEWAY_MAX_CLIENTS 2 defines how many controllers (eg Home Assistant) can connect to the gateway, not how many sensors/MySensors devices.
And yes, you can have multiple TCP gateways in HomeAssistant. I got an NRF24, an RFM95 long range and a RFM95 short range gateway (all based on ESP32) on the same Home Assistant.
Just for completeness: the right way to do this is to add the json under ~/.platformio/boards and the other files as described in https://community.platformio.org/t/how-use-a-same-chip-but-with-different-environment/18082/4
I found procedure gatewayTransportInit(), it works great. However, I cannot find a procedure that will enable detection of a network connection at level mysensors. I noticed that disconnecting the network plug or resetting the W5500 (37 pin to ground) changes the device's IP address to 0.0.0.0 - then I call gatewayTransportInit() - but mysensor's library must have such procedures - please tell me how to diagnose ethernet connection.