I have the same issue as you, maybe you're using an AV receiver as sound output through NVidia or AMD HDMI HD audio out as me.
I can only select more than that, using only the TV's speakers, or the headphones. This way I can also enable HDR, but is really washed out, almost no color.
I tried changing the settings and then set the config file as read only, guess what, just for that, battle eye shuts down the game, or it starts using your last "working" settings, and 720p again. I'm now going to try one last thing, I'm using just one HDMI all to the AV, and then to the TV, is this doesn't work, end of Beta for me, and game on hold until they fix this.
I will tell if this solution works.
PS: For those who hadn't read my post, and may think "just go with the headphones", I have a health condition, and cannot use headphones for more than a couple of hours.