AX
This repository contains hardware and software for the AX5043 and AX5243 radios from AxSemi (now ON Semiconductor). They are probably the same die, but the AX5243 has fewer pins.
There is hardware for the Raspberry Pi, C.H.I.P. and a 2mm pitch breakout board.
The software has both C and Python APIs, and can be used without the cumbersome Ax-RadioLab GUI tool. Not all features of the radio and supported yet.