FrSky is not making things simple with R9 long range system. New firmware appears quite often and there is no way to flash receivers over the air. You can use some PC software, passthrough from FC and things like that, but from my perspective, as long as you can get to the receiver itself, the simplest way to flash R9 Slim and R9 Mini is to actually connect them to Taranis or Horus and do it from the radio itself. How? Like this!