“Even when you run a latest-gen GPU with latest drivers, the monitor does not reliably show a picture after a suspend/resume cycle.”
Dell’s 6K U3224KBA needs about 34 Gbps to run at 60 Hz. DisplayPort 1.4a offers 25 Gbps, so full resolution depends on Display Stream Compression working in your GPU and driver. The older 8K UP3218K needs two DisplayPort cables and in practice only works with nVidia cards. Dell fixed a monitor that needs two cables with one that forgets to wake up.