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.

Hey, do you have plans to open any communities into Lemmy?