I just bought the ProArt 6K for my 2019 Mac Pro but cannot get it to output at 60Hz. Has anybody else encountered this problem or have any potential solutions? I’ve tried different cables, ports, etc. with no luck.
On Apple's support page they list the first GPU to support Display Stream Compression (DSC) as the AMD Radeon Pro W5700X.
So you need that, or a later GPU, to get 6K over a USB-C Alt-mode monitor.
Earlier GPUs had to have a Thunderbolt 3 display to get 6K.