Do not despair @antonical!
Once you get your Waveshare or equivalent, and can get serial data from F1/F2 into your router (thence into your laptop or RPi or whatever), you should be able to programme HA (via @pantherale0’s HA Integration) to do your bidding automatically, without the need for the MIM-B19N and any Modbus coding 
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Or, if you don’t actually need automation (only monitoring) you can download SNET-Pro2 (if you want to be able change settings like FSVs manually from the comfort of your laptop) and/or @PeterX’s NASAmonitor (if you just want to watch what’s going on).
If you do want to persist with the B19N, have you read @Sykes’ useful write-up starting at Recommendations for running a Samsung 6th Gen with Octopus - #15 by Sykes but developed more in the subsequent posts? Between them, @Sykes and @toadhall seemed to clear a lot of jungle and maybe some of it might help your exploration…