@MattFox For other folks who come to this thread, I was able to use the Prologix GPIB Ethernet Adapter: https://prologix.biz/product/gpib-ethernet-controller/
I have a working set of Mango Configs that I've got working to talk SCPI using the GPIB <-> Ethernet device servers to make this work. I originally tried to get this working with the Serial data source, but ran into a host of issues related to this.
Mango's quite versatile, but apparently the Serial data source chokes on SCPI-style commands- One reason was noted by @MattFox earlier in the thread, but it's also part of a problem with SCPI: Mango expects all data sources to return data, and some (many) SCPI commands don't actually generate an acknowledgement.
The GPIB <-> Ethernet adapter has the same problem, but the timeouts are faster, and you can use a trick in the Prologix device (++auto 1) to basically stream data into mango in Real Time.
The Mango config I put together for this is quite large, but if you're looking for SCPI interfacing, I'd imagine this script would work well for Native Ethernet as well as Vintage GPIB devices using an Etherent <-> GPIB device.
The Prologix one I linked above is the more affordable of the choices- you can just telnet into it, and issue commands, and it spits stuff back. It's actually quite cool.