My WiFi drivers fail from time-to-time, usually after a Kernel upgrade.
For future reference, this is the series of commands I run to fix them.
Source: https://gitlab.com/emrose/xps13-7390_debian/-/issues/5#note_240886447
git clone https://chromium.googlesource.com/chromiumos/third_party/linux-firmware chromiumos-linux-firmware
cd chromiumos-linux-firmware
sudo cp iwlwifi-* /lib/firmware/
cd /lib/firmware
sudo ln -s iwlwifi-Qu-c0-hr-b0-50.ucode iwlwifi-Qu-b0-hr-b0-50.ucode