The only way of "upgrading" is installing LineageOS 22, which will give you the equivalent of Android 15.
Since LIneageOS re-uses most of the device drivers from stock Android 9, it is unlikely that audio or camera quality will be improved. At least I do not know of any such updates.
That being said, a recent LineageOS will give you all those Android security patches since 2020, which is of quite some value in itself ...