Is there a way to add packages (dumb question, I know: install RPMs inside the SD card) from my PC and before inserting the SD card in the Raspberry? Something like a cross platform rpm installation. Maybe not.

My question arises from this fact: I'm unable to use the ethernet interface. I have only a wifi connection. So while I'm able to copy the related file into /lib/firmware/brcm/brcmfmac43430-sdio.txt during the SD card setup, I am still unable to use the wifi once booted the raspberry up, due to the lack of networkmanager wifi plugin and wpasupplicant.

Do you have some hints? This is not so critical, it is just a curiosity. Somehow I can retrieve an ethernet connection to install the required packages.

Ciao