The Denon/Marantz Dolby cross up mixing restriction is annoying for sure, but so is the Integra/Onkyo/Pioneer DD 5.1 surround channel info reroute to surround back speakers.
It is as though there are different Dolby license packages out there and each one of them comes with its own peculiar behavior.
Denon/Marantz at least include DTS Virtual:X all the way up the line but Dolby signals will need to be decoded and output as multichannel PCM at the source if at all possible to do so. Yet, it works with DSD signals.
The Onkyo web setup should really be considered by those mixing older devices with new HDMI 2.1 devices. Each HDMI port can be configured just so.
I’ve come across threads in various forums concerning Dolby Vision and those that want to turn it OFF but cannot do so in their TV or connected device to compare it to HDR10+ or HDR10.
The Onkyo web setup allows one to turn ON or OFF various features in the “Limit Mode” section of the web setup. Turn OFF Dolby Vision in a given HDMI port, and it will no longer be available for output to a connected TV using a device connected to the selected port.
Anybody still using an older HDMI/HDCP specced Oppo player or an even older Toshiba HD DVD player may have had issues with picture and/or sound output when upgrading to a newer AVP/AVR. The Onkyo web setup is a marvel here and I was able to properly configure ports for both my old Oppo and Toshiba players. I couldn’t do it using certain newer Denon or Yamaha receivers.