If you’re interested in something that doesn’t even exist, and should be more-or-less straightforward:

Music/podcast app that will accept VST plugins (there are many FOSS ones, as well as non-FOSS ones) so that we can compress/limit the sound range on podcasts while in the car. Or even a built-in compressor/limiter that’s based on FOSS compressors.

I was listening to a hysterical podcast episode between three people, but one of mics was way louder than the other two. I had to take it into Pro Tools and fix it myself before listening to it.

There are apps that allow EQ, but none that do actual compression, from what I can tell.

I use Mac for work (post audio) and Gentoo for fun on an Intel machine.

MacOS does not do well if you dig in to it like it’s a Linux box.