I know this doesn't help but I think the file picker is by far the worst feature Linux has ever had. And our opinions are quite common among Linux users.
It isn't actually a file manager. It is called a "file picker" and has been a reason to rant as long as I can remember, so close to a decade.
Kali isn't meant to be a desktop OS. Use it only in VM or in a spare rig. It is meant to be a toolbox. So dual boot it with your daily driver OS or use in a VM.
Your Mac can take Linux just well: https://djharper.dev/post/2020/06/07/running-linux-on-my-macbook/
For your 300 bucks budget look nothing else than Thinkpad T480 or HP Dev One. T480 will need replacement batteries if not replaced yet.
There's an app called BlackHole, but the music library it provides is very small and oriented in music from India.
Hey, do you have plans to open any communities into Lemmy?