Last summer Manjaro released usual heavy update and suddenly wifi on my old spare mbp was gone. Luckily digging around I found that a firmware was available in aur so I had to just plug ethernet in, install the package and reboot the system. But then another smaller update out of blue made system unbootable so instead of doing "forensics" I went by the easiest way of reinstalling the system and wifi again was working out of the box.