If there are Linux drivers for your Dell GPU Card it should work.
Looking at AMD Download page for the RX 640 it only shows Windows OS drivers but none for Linux.
Here is AMD latest AMDGPU Linux Drivers: https://www.amd.com/en/support/download/linux-drivers.html
Looking at the "Release Notes" for each of the Linux OSes it show being compatible with the RX 400 and 500 only though. Not sure if it is compatible with the RX 600 series GPU cards.
This is what it shows under "Compatibility" for each of the 3 Linux OSes:
Here is Dell's Support AMD driver for your Dell RX 640. But it shows no Linux Driver to install: https://www.dell.com/support/home/en-us/drivers/driversdetails?driverid=rmp33
Here is a Linux Ubuntu website about installing AMD Radeon Drivers: https://linuxconfig.org/amd-radeon-ubuntu-20-04-driver-installation
Also from Debian on how to install AMDGPU Linux Drivers: https://linuxconfig.org/how-to-install-the-latest-amd-drivers-on-debian-10-buster
Here is a Ubuntu Website with Certified Dell RX 640 PCs that uses Ubuntu 20.04 LTS 64 Bit: https://ubuntu.com/certified/component/821
Was this you asking the same question at Linux Mint: https://forums.linuxmint.com/viewtopic.php?t=417516