firmware installation problem with ASUS X540M (rtl8732BE)

[Joerg Kampmann <kampmann@ibk-consult.de>]

In order to install the buster-Debian-version on the above notebook (no 
LAN, no CD) seems to be difficult. I tried various approaches. It always 
sticks at the rtlwifi/rtl8723xxxx directory - which is to my knowledge a 
subdirectory of the /firmware directory. I generated an USB-stick (16 
GB) with unetbootin-linux64-661.bin from an ISO-image file containing 
all modules not requiring a netinstallation (small CD).

Question: where are the *.bin files stored for the system finding them?

Thanks for  a clear answer

Jörg