Apple - Missing Wifi interface after upgrade to Catalina

I had the same issue. Updated to catalina overnight and in the morning wifi was not working. I reinstalled catalina from Recovery again. Now wifi is working even though System Information App still shows (null) for Network -> Wifi entries

So thanks to Giovanni Caporaletti for posting and referencing this issues on the apple communities forum. I've as at today been able to update to Catalina and have wifi working. The solution can be found here

but to prevent it being lost for whatever reason I'll repost it below:

  • Download the modified files (thanks Alex!) and unzip > you get a folder named WiFi_kexts.
  • Boot into Recovery Mode: restart your computer while pressing and holding cmd+R
  • Open Utilities > Terminal via Menu Bar.
  • Type csrutil disable and hit return
  • Type reboot and hit return > computer reboots normally
  • Open Utilities > Terminal and enter cd and hit the space bar (don't hit return)
  • Drag the folder WiFi_kexts onto the Terminal window and hit return.
  • In Terminal, enter sudo mount -uw / and hit return, then enter your user password and hit return.
  • Enter sudo cp -r IO80211Family.kext /System/Library/Extensions/ and hit return
  • Enter sudo cp -r IO80211FamilyV2.kext /System/Library/Extensions/ and hit return
  • Right-click on Kext Utility in the folder WiFi_kexts and choose open, click open in the following dialog, authenticate with your password
  • Wait for Kext Utility to complete – this took maybe two minutes on my setup, and I got an error message in the end, as well as "All done"
  • Reboot your computer and enjoy Wi-Fi in Catalina If you want to turn on SIP again you can boot into recovery mode again and enter csrutil enable (hit return) reboot (hit return)

In summary I had to get the Wi-Fi kexts from Mojave, copy it to /System/Library/Extensions and then run the Kext Utility to do its thing after which I had my Wi-Fi back.