Newbie alert: Getting errors both in Webapp and Node-RED

[Mastiff]

To clarify, I'm a newbie with the Node-RED plugin for SignalK, I'm not a newbie with SignalK (been using that for a couple of years) or Node-RED (been using that for close to ten years for my smarthome and smartcabin). So I installed the plugin to my Pi, which runs SignalK, Node-RED, Home Assistant, a wifi router and a bunch of other stuff. I do a bit of Python, LUA and a tiny bit of YAML and JSON programming for the systems. I am also running a bunch of ESP-32, I think I have 8 in my 24' open pilothouse aluminium boat, which I use for fishing with shellfish pots and some rod and reel fishing. I wanted to have the possibility to log a few things from the plotter in Home Assistant, so I installed the Node-RED plug-in to send it from there to Hass with MQTT messages. But I get no joy, I'm sure it's an idiot mistake. I had a problem finding good info for the plug-in.

First of all I want to use the Node-RED instance I'm already running. Any 2 version won't work on my system, because I am running a few older things for my regular Node-RED, so I don't have the libraries that version 2 demands. So here is what I did: I installed the plug-in and tried to set it up, screenshot:

   

I don't get where that "unexpected token u" comes from, but I have a sneaking suspicion that it has something to do with my original Node-RED installation.

As for the Node-RED flow it's very simple:

Code:

[{"id":"cbbdb1aa.0c773","type":"signalk-notification","z":"85e2b9a.f39d948","name":"Dybde","notification":"environment.depth.belowTransducer","state":"any","x":115.66667175292969,"y":318.66668701171875,"wires":[["690f702.8d1ea9"]]},{"id":"690f702.8d1ea9","type":"debug","z":"85e2b9a.f39d948","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":320.66668701171875,"y":319.6666667461395,"wires":[]}]

In the Webapp I get: Cannot GET /undefined
And in Node-RED I get:

TypeError: Cannot read property 'subscribe' of undefined"

Can somebody please put me out of my misery here?