(Note: It's not a detailed guide, just a rough guide.)

- install linux headers kernel 4.19. make sure your kernel is 4.19 too. Reboot. (Doesn't work for me linux kernel 5.5, 5.4, with linux header 5.5, 5.4, etc.)
- download https://github.com/jeremyb31/rtl8822bu the driver zip file
- unzip the file, make, sudo make install
- shutdown pc, plug in usb wifi adapter
- start pc, start network manager
- choose the wifi ssid you want to connect, enter password

- restart router (power off, power on) *(This step is for 5Ghz wifi band, cannot connect to 5Ghz wifi band if I didn't restart router. Otherwise I could connect to 2.4Ghz without restarting the router)
- done

P.S. - Tested on my pc just now, which is running manjaro linux i3 distro, and using tp link archer c6 router. It works. There might be required packages which are left out in this tl;dr guide, 'cause I had tried installing it beforehand using other methods, and maybe the required packages had been already installed on my pc because of that. So when I do the above steps, all my necessary packages were probably in my system. Except the linux headers, so... good luck.