Extremely Simple fix:
Plug your hdmi out for video directly into the monitor/tv from gpu. Why the fk should your receiver fck with the video? No, leave the receiver out of it..
( if you played fighting games where every single ms of lag counts, this should already be a no brainer)
Use a 2nd out from your gpu into the receiver for audio only.
You are right that a simple fix could be applied, no doubt about it. And I know that many new owners have tried to resort to it, being out of other choices. But that's not the point here and such fix defeats the purpose of using new technology that has been so widely and frequently advertised, including in more expensive models. HDMI 2.1 apprears to be in the top three features in official adverts and it carries 'heavy lifting' as a selling feature. If someone buys a new AVR for hundreds or thousands of $/£/€ after exposure to such adverstisement and numerous presentations of products throughout the summer, one would expect top functions to perform reliably, rather then being told to apply a simple fix. This temporary fix was officially recommended by Sound United too. It's not a fix, let's be clear about it. It's an embarrassment for the company that was not willing to wait long enough for a HDMI 2.1 chip to be properly tested with engineering samples of new sources.
It's not about gamers only either, as high frame rate is just one of several benefits of HDMI 2.1. Another one is throughput beyond 18 Gbps via RFL lanes, e.g. 4K60 RGB 10 bit content, where input lag is not that relevant. There are professionals and enthusiasts who would like to run their graphic simulations and high quality video projects with lossless music in the background with one simple connection that was supposed to work out of the box, rather than apply temporary workaround after spending so much money on new gear. Their new AVRs have one single HDMI 2.1 port, and it does not work properly. It's simply not acceptable. Many users also have one single HDMI port on their PCs, the one on GPU, and do not want to play with DP-HDMI workarounds, or are not aware of them, just to be able to extract audio. It's yet another hassle to make things work, yet another product to buy.
Finally, there are customers whose TVs or monitors do not necessarily have eARC function or their eARC is buggy, as we know from thousands of posts in different fora. Problems with eARC have plagued dozens of devices across the board for several years now and those issues frustrated so many people. The feature was supposed to deliver only one single thing - lossless sound back to AVR. Some new and popular TVs do not support pass through of DTS sound either. So, 'simple fix' is not that simple in specific configurations of home theatre or in professional studios.
Your practical advice can work for some users for time-being, which is fine, but it is not surprising that customers are increasingly angry and dissatisfied with multiple malfunctioning features that cannot make their audio-video systems running reliably.
