No wifi adapter found on Linux Ubuntu 18.04

 Run this command:

rfkill

D TYPE      DEVICE      SOFT      HARD

 0 bluetooth hci0   unblocked unblocked

 1 wlan      phy0   unblocked unblocked

If the wlan is hardware blocked, need to goto BIOS settings and change the wireless adapter to enabled.

For example, the Asrock X399, need to goto the BIOS and find South Bridge to change the wireless from Auto to Enabled.