You can try to install newer firmware manually.
Open a qube with internet access and clone the linux-firmware repository:
git clone https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware
Then copy the directory to kali-core:
qvm-copy linux-firmware
Open a terminal inside kali-core, then go to /home/user/QubesIncoming/<qubename>/linux-firmware
Copy all iwlwifi related firmware to the /lib/firmware directory:
sudo cp iwlwifi-* /lib/firmware/
Turn off the kali-core template, start up your kali HVM qube, connect your NIC to it and see if it works.