Buying a Signum just for a TCP gateway is a massive waste of money.
As it also contains a version of HomeAssistant, with all the wonders that provides. (Logic engines and front end solution)
Can I strongly suggest that you run a little bit of gateway software on the machine that is currently hosting your full version of HomeAssistant, between the USB device and all your required connections.
In your version of HA, use the network bridge option and point it to 127.0.0.1 and whichever port is needed. {6000, 27015, 3788 etc, with or without TLS / SSL & password}
This will mean that you can run HA at the same time as Velbuslink (and anything else).
You can also use the logging screen in Velbuslink to check the activity of HA.
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There are Debian scripts to make the installations really easy.