This isn't a forum where team members routinely visit or post, it's primarily user to user with some oversight by support staff.
I dove into Premiere's full color management ingesting through export last year for a presentation I gave in the Flanders/Mixinglight booth at NAB, and a pair of tutorials on Mixinglight.com. Spent several hours on the phone, screen sharing, and in person with then-color engineer Francis Crossman.
Premiere can work just fine with Rec.2020 as-is internally. Set the scopes panel to Rec.2020 and in the Lumetri panel, turn on the HDR setting.
That isn't the problem.
The problem is no internal monitors work properly with media above 105 nits or so. Not Source, Program, nor Transmit Out.
They just quietly added an option in Preferences to enable extended range monitoring which on a Mac supposedly allows resetting monitors such that you can work with "extended range" media, maybe as high as 500 nits. I'm not on Mac so I haven't tested that.
For full HDR, you have to get the signal out of the OS, and they put the "calls" out for that over a year ago. The only company responding is AJA so far, no BlackMagic gear has had the firmware altered to "see" Premiere.
So for Mac, it's the io4k unit connected to the HDR monitor via HDMI, and set to pull the Premiere signal.
For PCs it's the AJA Kona 4/5 PCIe cards, again connected via HDMI to the monitor.
They are around $1800 each, but then, any actual grading monitor that can properly reference for HDR is still above $28,000.
And no, from all professional testing the new Mac XDR monitor isn't even close because of dimming/blooming issues. It can handle bright scenes relatively ok, but dark segments lift horribly if any middling/brighter pixels are in a relatively large neighborhood. It can't maintain over 1,000:1 contrast with mixed material.
Though ... set properly, it's the best Apple monitor for SDR work, nearly matching a Flanders or Eizo for overall levels. Though screen uniformity ain't even close.
The Premiere developers are working on revamping the code to handle user choices for Rec.709, Rec.2020, and full HDR. But they never tell us when such changes are coming. So ... we'll know about it when it "drops".
Neil