After installing debian buster on my Dell XPS 13 9350 (2016), Wifi wasn't working. The boot messages from Linux were showing errors about loading the firmware for the broadcom wifi chip.
Wifi was running fine out of the box for Ubuntu 20.04, CentOS and FreeBSD, so I copied the broadcom firmware
from ubuntu to
/usr/lib/firmware/iwlwifi-8000C-36.ucode in Debian Buster.