There's also the excellent https://www.nand2tetris.org/

From basic computing gates all the way to running tetris. It taught me so much of the lower levels.

Also a comment as a former Gentoo user of 7+ years - the performance is there - 5-15% maybe. I honestly don't think it's noticeable, it never was to me, but what you learn using Gentoo has served me very well.

I moved on as well. I'm too old to deal with fixing things and all the waiting, I just want it to work haha