Just built a new gaming computer. Having the same issues listed above. My speakers are the Logitech Z906 5.1 system. I'm using the standard 3.5mm aux jacks on both the computer end and speaker end. As stated above, the EQ has been moved to the "premium" audio software, in my case it's Asus DTS. However, that software doesn't work when using the multi-channel output (three 3.5mm jacks) because it's really designed to enhance a basic stereo signal. This means I don't have access to the EQ settings (which BTW are just 5 bands in this software, not 10). Switching the settings in Win11 to a stereo output gives me access to those audio settings, but I'm locked out when I switch back to 5.1.
Yes iTunes, Media Player, etc. have built-in EQ's, and that's great for when I'm listening to music. But what about when I'm watching Netflix, or Disney+, or YouTube, or playing games? It seems I'm stuck with ugly sounding flat audio.