Audio quality similar to Steam Deck solution, there is a built-in EQ settings.

There should be a "Realtek Audio Console" app installed on your Windows. Open that, disable Omni Speaker(this sacrifices too much bass/mids to me for wider sound stage), then set EQ to this:

Viola, miles better than default setting, max volume weaker than SD but good enough for indoor, no idea why Lenovo let the default that way.