New testing shows DisplayPort 2.1 is very picky about the monitor cable you're using
DisplayPort 2.1 GPU connected to DisplayPort 2.1 monitor. Result? DisplayPort 2.1 connect. Right? Apparently not, according to Monitors Unboxed. At least, not always.
Now, without getting bogged down in the details, the main attraction of DisplayPort 2.1 is bandwidth and lots of it. That means not only higher resolutions, refresh rates and colour depths, but also those higher resolutions, refresh rates and colour depths without using compression.
DisplayPort, of course, optionally...