Use an adaptor then from whatever other pc out port to the hdmi cable.
Those are OEM class cards, so really Dell need to sort your problem.
Maybe it only works on dell supplied drivers(there are no direct drivers for rx 580x from amd).
As for me having to look up specs, INFORMATION REQUIRED WHEN POSTING A QUESTION
Ryzen 5 5600x, B550 aorus pro ac, Hyper 212 black, 2 x 16gb F4-3600c16dgtzn kit, NM790 2TB, Nitro+RX6900XT, RM850, Win.10 Pro., LC27G55T..