Out of the box, nothing.
The system is able to find the hardware, you can install drivers for it trough the driver-manager, but those does not work any more.
|What doesn't work:|
The "Alfa Network AWUS036ACH" is branded as a good wifi-adapter for Linux, but on Linux Mint 19.1 and 19.2 it is not a good choice. The system is able to find the hardware, install drivers trough the driver-manager but it's completely non-functional out of the box even with the drivers you can install trough the driver-manager.
I had to acquire 3rd-pary drivers from an other source in order to get it working, and it required me to lock the Linux Kernel at 5.0.0-20, any update to the kernel would break the driver and render the wifi-adapter unusable again.
|What was done to make it work:|
I followed this tutorial and installed some 3rd-party drivers that are more updated then the ones the driver-manager can provide.
The hardware does work after installing these 3rd-party drivers, following this tutorial;
However! In order to keep these drivers working,you need to freeze any further Kernel-updates, if the kernel gets updated then these new drivers will break, rendering the wifi-adapter useless again.
Here's the subject discussed on the Linux Mint Forum!