Dear Bernhard,

Thank you very much for your clear and helpful report!

> I tested the following:
> 
> 1. Copy file brcmfmac43430-sdio.AP6212.txt from upstream to lib/firmware/brcm

so indeed it is a bug that we don't ship this one from upstream,
will fix this in next Debian upload.

> 2. Create symbolic link named brcmfmac43430-sdio.sinovoip.bpi-m3.txt to the AP6212-file
> 3. Create symbolic link named brcmfmac43430-sdio.sinovoip.bpi-m2-ultra.txt to the AP6212-file

this should be reported upstream, so that everyone takes advantage of
it, hence adding linux-firmware mailinglist on Cc, happy to cook up
a patch next 24hs.
 
> After that, the wlan0 interface is available and scanning of the WLAN-ESSIDs works.

great!

 
> Please either do it like described above or add the files directly instead of the symbolic links.

The symbolic links are better than duplicated files, but there seem to
be on the Debian side an opened can of trouble on them, see #982757
(I'll post there soonish)
 
Thank you for the kind words, the test and your report!

-- 
maks