it doesnt look good for you, theres a lot people with your speaker issue (realtek alc287+lenovo)… try these links:
https://forum.manjaro.org/t/headphones-work-but-laptop-speakers-do-not/93362
and also try this patch:
https://wiki.archlinux.org/title/Lenovo_Yoga_7i#Speaker_audio
even when its written there that its included since the 5.14 kernel, youll have nothing to lose