It looks like the fine people over at aircrack-ng
have a rtl8814AU repo:
https://github.com/aircrack-ng/rtl8814au
They know what they're doing and seem to properly maintain them :)
You should use that one instead of this repo.
This repository contains a driver for the rtl8814AU chipset.
The original downloaded archive indicated that kernels till version 5.1 are supported.
With some adjustments I've made it work till 5.5, but it fails to compile against 5.6 (on Debian).
I don't have a device with this chipset, just happen to stumble upon the driver.
That is one of the reasons I have no intention of spending time on it.
You're of course free to use it, fork it and all the other freedoms granted to you by the LICENSE.
But don't expect me to spend time on it.
The best you (all) can do is:
This is nothing personal or something like that. My time is limited and maintaining this/a driver repo is not the best use of my time. I'm not dumb, but I'm not a C coder, let alone a kernel hacker.