I got that problem on a ROG Strix G733ZM. The solution was to install "hdajackretask" (sometimes in an ALSA tools package, sometimes elsewhere), select "ALC285" and "show unconnected pins" and map pin 0x14 to "Internal Speaker" and pin 0x1e to "Internal speaker (LFE), then install boot override and reboot.
Oh and after reboot I went to Configure Audio in KDE and selected a profile.
I found it randomly online, don't remember where. I wish I knew how those pins were discovered in the first place because it may well be different for different laptops and also I really want to know....
Oh BTW, in case you need to know: My microphone was having an awful lot of static noise. The trick was to 1) reduce microphone volume to 50% and 2) enable the ladspa-rnnoise noise filter in pipewire (it was already in my distributions repo). I checked in Windows and it sends the mic through an "ASUS AI noise filter" - so they've basically saved money on the hardware and are doing the same thing.