This blog has some info on Apple and privacy.

https://sneak.berlin/20200604/if-zoom-is-wrong-so-is-apple/

https://sneak.berlin/20201112/your-computer-isnt-yours/

https://sneak.berlin/20201204/on-trusting-macintosh-hardware...

https://sneak.berlin/20210202/macos-11.2-network-privacy/

Two comments from the same author on M1 Macs.

https://news.ycombinator.com/item?id=25958422

https://news.ycombinator.com/item?id=25778750