Last year we started to see the first receivers roll out with HDMI 2.1 ports that could support 120Hz refresh rates and up to 8K resolution. However the early devices have had compatibility issues with other hardware — namely the Xbox Series X — and it looks like the fix will be pretty complicated.
As Forbes and HD Guru point out, Yamaha, Denon and Marantz all sell receivers that have had these compatibility problems that gamers noticed once the new consoles started rolling out last fall. Denon and Marantz are both brands owned by Sound United, and they're going to fix it by providing an extra hardware adapter to sit between the Xbox and their receivers. The SPK618 will "correct" the HDMI data from the Xbox so that it's passed to your 4K/120Hz ready TV while also playing audio. Owners of affected receivers can order the box starting on May 15th by checking with Denon or Marantz.
As for Yamaha, so far it's advised gamers to connect their consoles directly to the TV — which can have its own issues, as we've experienced — and use HDMI eARC functionality to feed audio back to the receiver. It also said "We will address the reported HDMI 2.1 issue via these planned future updates in order to provide customers with the best solution available."