On the manufacturer's tech specs page, for this product, they say:
* A chassis with an HD audio module in the front panel is required to support 7.1 Surround Sound audio output.
** The LINE OUT port on the rear panel does not support spatial audio. If you wish to use spatial audio, make sure to connect your audio output device to the audio jack on the front panel of your chassis or use a USB interface audio device.
I'd suggest downloading and reading the owners manual from their web site, for more details:
The ROG Strix X870E-E Gaming WiFi elevates builds with 18 power stages, DDR5 slots and extensive PCIe 5.0 connectivity. It features five M.2 SSD slots with heat
rog.asus.com
If you don't have a chassis with HD Audio front panel connectors or don't want to plug your speakers in there, I wonder if someone makes an I/O bracket that you can mount in the rear of a case. I haven't read much, but I think that's what this poster is asking about:
Possibly relevant?