Will Whang designed a Raspberry Pi hat board (also a variant for Pi Zero) acting as a LoRaWAN gateway/concentrator. It directly uses the Semtech SX1301 and SX1308 digital baseband chips. The SX1301 is suitable for outdoor LoRaWAN macro gateways and the SX1308 fits for indoor LoRaWAN pico gateways.
He provides Eagle schema and Gerber files etc. in the respective GitHub repository (see below) and is also selling an assembled kit on Tindie. Kudos!
Announcement on the TTN forum