long story longer,
i currently have a k5000 4 port card, which only two folks had any input on when i had a question before, which has been having problems and is only getting older. i am trying to find a replacement. so two questions up front,

from best buy:
XFX - THICC II Pro AMD Radeon RX 5500 XT 8GB GDDR6 PCI Express 4.0 Graphics Card - Black
Model:RX-55XT8DFDR
SKU:6395411

first question - anyone have experience with this card and linux?

second question -
amd has an ubuntu driver. i use slackware, but does anyone know what (or maybe where) that driver will look for something in ubuntu that is not in slackware, open gl is open gl across any platform right?

and or also, if not the above...
does anyone use a 4 port video card with linux that has a good driver that has had a good experience working with it (installing and also relatively trouble free)?
thank you

For current distro releases (18.04, 19.10, 20.04) and GPU models? I was under the impression AMD stopped providing proprietary drivers quite some time back, maybe close to two years ago, and that AMD back then decided to do what Intel has been doing at least 5 years - paying its Linux driver writers to code the FOSS drivers that all Linux distros provide as core packages. This for AMD GPUs means xf86-video-amdgpu (the upstream name of the package containing the amdgpu DDX for Xorg and Xwayland, which Debian and its derivatives inexplicably rename to xserver-xorg-video-amdgpu) is coded primarily, if not entirely, by AMD funded people.

??? Look for something? What would any driver be "looking" for? Is this some reference to Ubuntu's system installation program?

FWIW, current FOSS drivers on recent GPUs seem to be rather capable: https://susepaste.org/view/raw/81396694

I think he's referencing the AMDGPU PRO extensions that AMD releases. These are not needed unless you want OpenCL support. OpenGL is included in the kernel with AMDGPU driver. You will just need the correct firmware for your card, and a new enough kernel (5.3+ MINIMUM, 5.5+ preferred) that the amdgpu driver will be new enough in order to work with the card.

As to the rest of the questions, no idea. Sorry, never used more than 2 monitors at once due to lack of space.