 2 laptops (Lenovo and Dell) on Jammy.  Brightness and battery widget in the tray and working fine, as well as the brightness control function keys.
 Nothing "special" required to enable functionality so I am not sure how to advise.
[11:49] <BluesKaj> Hi all
[12:05] <yofel> so 2 systems now upgraded to jammy here as well with the upgrade going as well as one could hope. Only upgrade issue was that on one laptop firefox was broken afterwards because my network connection was dead during the upgrade so the snap couldn't be installed.
[12:05] <yofel> the brightness widget works fine on both laptops for me (both intel/nvidia-prime)
[12:06] <RikMills> yofel: hi, and thanks for that :D
[20:12] <valorie> hmmm, that is most mysterious
[20:12] <valorie> so the "brightness bug" is only me and nikola