All of their current lineup allow for the conveyances of HDR, but Yamaha do not now unfortunately still manufacturer a directly comparable model to your RXV777. The closest you'd get to it is the RXA880. This would give you the same pre outs, phono stage and dual HDMI outputs as associated with your older reeiver as well as the same build attributes associated with the Adventage Yamaha models.
The receiver includes HDCP 2.2 compliance as well as the ability to passthrough HDR10, Dolby Vision and HLG HDR. You can buy one for about £730.
A slightly better option would be to look at last years RXA1070 which is a better receiver than the RXA880 and not that much more expensive due to it being discontinued and discounted. You can still get one of these for about £800:
The advantages would be its use of better DACs and its superior processing power. The latter would allow it to apply DSP Programs and processing to 3D imersive ahdio formats such as Atmos and DTS:X. The models below it haven't this ability.