In Linux Mint Xia ver.22.1, it is now possible to use the wifi5 by a standard driver (module) compatible with rtl8812au.
[1] Basic steps:
Installing the standard driver
After starting the system and plugging the USB wireless LAN adapter, you will be asked whether you use the standard module. If you select "Use," the rtl8812-dkms is installed then the wifi is connected.
[2] In case of connection falure of the wifi by use of the above steps:
[A]If the wifi is soft/hard blocked, remove the soft block on the wifi.
$sudo rfkill list
0: phy0: Wireless LAN
Soft blocked: yes
Hard blocked: no
2: phy2: Wireless LAN
Soft blocked: yes
Hard blocked: no
$sudo rfkill unblock all
$sudo rfkill list
0: phy0: Wireless LAN
Soft blocked: no
Hard blocked: no
2: phy2: Wireless LAN
Soft blocked: no
Hard blocked: no
[B] If the wifi is hard blocked yet:
1.Initializing the BIOS
If your PC's BIOS has no option to initialize the wireless LAN, try the CMOS-battery-pull-reset the bios, as follows:
2.Remove the CMOS battery, and insert it again (1).
Note:
(1) Some PCs have wireless lan toggle switches.