did you ever changed the grub-config ? there is a workaround for lenovo. please read the links below carefully, but please ask before you change something that will cause pain. one solution is described here
but it differs from the solution here, because one is using intel_backlight but the other one uses acpi_video
https://wiki.archlinux.org/title/Lenovo_Legion_7i
how to edit kernel parameters is described here
https://wiki.archlinux.org/title/Kernel_parameters
please read carefully and if you feel firm to go on post back to prepare the next steps
hope this is helpful for you
P.S.: the tip of @linux-aarhus might be more actual. you can give it a try.