You don’t need an app to not use the extra pixels Apple added on either side of the notch.
If you want the same appearance (and resolution) as a non-notch MacBook Pro, open System Settings, go to the Displays section, click Advanced... and toggle on “Show resolutions as list”, save that change, and then enable “Show all resolutions”.
Now select the resolution option just below your current selection. (The y-dimension will be slightly less, which equals the space added by the pixels around the notch.)
That's an okay workaround, but you lose part of your screen and create a thick top bezel.
As a laptop user, I want to use all available space, so what I do is to use https://topnotch.app/ (or a dark wallpaper) which makes the background of the bar black and until now I was using Bartender, which would display the hidden icons on a second bar under the original one when we clicked the icon. I barely noticed the notch.
I'm sure I'm missing something obvious. I ran Hidden Bar for months and the hidden icons only became visible left of the notch after clicking > maybe twice, briefly, and I could never figure out what I did differently. iBar worked immediately.
iBar (free at the App Store) so far does what I need.