No need to hunt INAV firmware mirrors. inavflight.net has the 9.1 download, the Configurator and the real documentation. That is enough for a first wing or quad.
INAV and Betaflight are different. Use INAV when you need navigation, a plane, a VTOL or a rover. I only download the flight-controller firmware, the Configurator and the 9.1 docs from inavflight.net. Old forum copies are not worth it.