airmon-ng

root@kali:~# airmon-ng

PHY	Interface	Driver		Chipset

phy0	wlan0		88XXau		Realtek Semiconductor Corp. RTL8812AU 802.11a/b/g/n/ac 2T2R DB WLAN Adapter

airmong-ng start wlan0

root@kali:~# airmon-ng start wlan0

Found 2 processes that could cause trouble.
Kill them using 'airmon-ng check kill' before putting
the card in monitor mode, they will interfere by changing channels
and sometimes putting the interface back in managed mode

  PID Name
 2678 NetworkManager
 2693 dhclient

PHY	Interface	Driver		Chipset

phy0	wlan0		88XXau		Realtek Semiconductor Corp. RTL8812AU 802.11a/b/g/n/ac 2T2R DB WLAN Adapter

		(mac80211 monitor mode already enabled for [phy0]wlan0 on [phy0]10)