Sadly, Sound United has not really "fixed" HDMI 2.1 in the Denon and Marantz gear. Their solution is a working one, but not complete.
The new Onkyo gear is supposed to be working out-of-the-box, but as yet I've seen no real review with measurements and I don't trust the chuckleheads of the YT Pop-Vid Squad.
The new Yamahas are waiting for a firmware update, and who knows what other surprises await.
You are correct about the currently available batch of Anthems and 2.1. I've heard their 2021 release was a little lackluster in terms of workability. We'll see if they can redeem themselves as the year wraps.
Several companies are offering HDMI upgrades which will require, most likely, shipping to a service center.