This is 2 separate issues with 2 different possible solutions.
First is audio and second is screen brightness. The GPU drivers do not manage the screen brightness so the nvidia driver is not the problem.
Please separate these issues into 2 different threads so each may be addressed appropriately.
I am not an expert in either so cannot provide useful suggestions other than this one.
This is at least the third thread on this topic here:
I made a post on that kernel bug tracker as well since there doesn’t seem to have been any action for a few months, but I don’t know what else to do.
Are there bug bounties one can post to incentivize faster fixes, or does one have to wait until a kernel developer buys a yoga pro or someone at lenovo starts to use linux?