[Solved] R9 380 on MacOS Catalina
When I plugged in the card it didn’t showed up in the status bar and in the system info it shows as a monitor (manufactured by AMD) when I unplugged it the system warned me to first remove it
And it couldn’t work for both internal display and external display
There's no official support in macOS for the R9 380. It will not be plug-and-play at all. You can try Purge-Wrangler and see whether this script would make it work in Catalina. Make sure to read the instructions to install legacy AMD graphics card support.