I'm not an expert on Linux and I've only swapped from NV to AMD cards a couple of times on Linux, but I've never had a good experience doing so and always ended up having to just install fresh. Unless you were using the open source NV drivers instead of the proprietary ones? Those ones are far less troublesome in terms of uninstall.
Can you post the output you get from this command?
sudo lshw -c video
mark@12700F-linux:~$ sudo lshw -c video
[sudo] password for mark:
description: VGA compatible controller
product: Ellesmere [Radeon RX 470/480/570/570X/580/580X/590]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 0
bus info: pci@0000:01:00.0
logical name: /dev/fb0
width: 64 bits
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom fb
configuration: depth=32 driver=amdgpu latency=0 mode=1920x1080 visual=truecolor xres=1920 yres=1080
resources: iomemory:420-41f iomemory:410-40f irq:169 memory:4200000000-43ffffffff memory:4100000000-41001fffff ioport:8000(size=256) memory:96100000-9613ffff memory:c0000-dffff