Possibly overkill since it uses cellular uplink instead of a LAN, but my company’s DIN Ranger fits most of your other requirements.
It only has one serial network, and the GUI is only available via USB connection for initial setup, but definitely on all other requirements.
Maybe you need to monitor modbus devices away from where a network is currently available and this is a win-win?
On the other hand, this does require that your MQTT broker is accessible to the internet at large, which may be a showstopper if your IT team doesn’t want to have to do security properly. Rangers support authenticating via client TLS certificates and can do security the “Right Way” if your IT is willing to work with it, though.
EDIT: If you need MORE connectivity on the modbus side but don’t need cellular, the people over at Opto22 are sharp and definitely work with Ignition a lot. I don’t know their product line as well, but SignalFire people have co-presented with them on technical webinars about Sparkplug and Ignition, and I’ve interacted with their engineers on Sparkplug committee discussions on occasion.