The use case, other than the appealing option for an wired ethernet, switched and VLANed UART, was to gain remote access to some solar panel gear in the garage.
It all speaks RS485 ModBus and apparently at least the most common registers are standard to some degree. Such that, and I really didn't expect this, different manufacturers displays will read others devices and vice versa. Would be interesting to see if there is a published "standard" set of these registers somewhere.
From what I'm reading however it doesn't sound much like it will be "plug and play", connect RS485 port, connect TCP, connect app to VCP driver.
I already have an RS485 monitor installed, it's an ESP8266 originally running my code, but now running someone elses more polished version. The downside is, it's "standard monitor" only. You can't modify the config registers.
The only way to change a battery charge parameter in the solar charge controller is to go down and connect the laptop to the thing with a USB/RS485 dongle. My laptop has recently expired, screens gone, not worth trying to use anymore. Not hurrying to get a new one. Un wiring it all, bring the controller to the PC and doing it that way is fine for a one off, not for fiddling and testing.
So one option is to write a specific Modbus TCP proxy in an ESP32 myself where I control both ends. It means it's Wifi rather than wired but that's fine for my use. This kind of roll-you-own can exclude 90% of the protocol overheads that I don't need and focus on making the EPEver PC app work.... or... just use the registers myself directly with a commandline client.