This was reported by user PETURBG on IRC:
[ 21.951985] iwlwifi 0000:03:00.0: no suitable firmware found!
Trying to install firmware-iwlwifi from the debian non-free repos shows it has the same files as vyos-linux-firmware so it errors:
Unpacking firmware-iwlwifi (20190114-2) ... dpkg: error processing archive /var/cache/apt/archives/firmware-iwlwifi_20190114-2_all.deb (--unpack): trying to overwrite '/lib/firmware/iwlwifi-3945-2.ucode', which is also in package vyos-linux-firmware 20191022
(vyos-linux-firmware should probably yave a Conflicts entry in debian/control for all the debian firmware packages it replaces)
Unpacking the firmware-iwlwifi and manually copying its lib and usr contents makes the missing firmware work:
[ 22.043622] iwlwifi 0000:03:00.0: loaded firmware version 126.96.36.199 build 25532 op_mode iwldvm
I'm not sure whether we should include this by default as it's in the non-free repo and I personally try to not use it if possible.