Xbox series X hooked into soundbar directly via 2.1 HDMI cable.
Soundbar hooked to HDMI port 4 on Q90T TV via 2.1 HDMI cable.
When switching from the SDR menu and launching a game in HDR, the screen blacks out during the switch. Then sound stops working. If I switch sound mode to another setting (IE adaptive to surround) the sound returns. I can then switch back to the original sound mode and it works...until it switches back to the SDR menu and the sound goes out until I do the above mode swap.
I also tried plugging the Xbox into the TV and using eARC back to the soundbar. The above sound issue isn't there. However, sometimes the sound drops while using the Xbox and it will return a second later.
The optimal set up for these devices would be to connect all of your HDMI devices directly to the television and then use ARC to the soundbar. I would also recommend trying higher quality HDMI cables.
I purchases a 4k player and the atmos still drops out when using eARC to pass-through. It happens 1-3 a movie. crackles and then a couple of seconds of silence and it comes back. I bypassed the TV and things work. I think there is an issue with the Q90T eARC and atmos.