This is probably a fairly vanilla SX1301-on-a-pi type of gateway. The main connection would presumably be to the pi’s SPI bus, along with another GPIO for the SX1301’s active high reset (high to reset low to run) which typically gets handled via a script using the /sys/class/gpio/… interface.
Try searching the filesystem of their image for a script referencing that, files like global_conf.json and so on. Also do a
sudo logread -f and see if you have messaged from a “packet forwarder” which is the main gateway software component.
If you can figure out that it’s an ordinary SPI interface, and identify the GPIO used for reset (either from their install or by tracing the interface board) then you can probably put their SD card on the shelf, get an ordinary Raspbian or whatever image and follow setup instructions for an iC880, RAK831, RAK833 or whatever and get things going in short order - there are also some “out of the box” pi images floating around that might just work or only need the reset GPIO changed.
Also worth referencing http://www.embit.eu/wp-content/uploads/Datasheet-EMB-LR1301-mPCIe_.pdf
Found there are the facts that this appears to be the later generation concentrator design with an FPGA, though that should probably be handled for you by the Semtech packet forwarder. It would appear that on this card the reset is the traditional PCIe active low, so a standard script written to talk to a bare SX1301 may need the sense with which it is driving the reset inverted.
I’ve not worked with a concentrator of the generation having the FPGA, so it would probably be worth spending some time to understand how the host interaction usually works there. Most of it should probably be taken care of by the Semtech code. It’s also possible that (if your area does not require listen-before-talk) the extra capability could simply be ignored.
Also the pins used for SPI are different than on something like a RAK833, though that probably won’t matter as long as you use the supplied interface board.
Worth checking if the interface board might be just a branded respin of http://www.embit.eu/products/oem-gateways/accessories/emb-raspi-lr130x-cape/ or at least seeing if there is any software setup documentation for that which might apply.