It really depends on your approach to learning things. If you’re looking for a systematic approach, I really like No Starch Press books for that sort of thing: How Linux Works or Your Linux Toolbox (for a more playful approach).
But in the end there’s really no substitute for installing Debian on bare metal and tinkering with it. I would really recommend Debian, because it’s the archetype of how Linux systems have been working for the last 30 years or so. Arguably, this is currently changing, but come to grips with Debian before you dabble in more modern approaches to system management.
It really depends on your approach to learning things. If you’re looking for a systematic approach, I really like No Starch Press books for that sort of thing: How Linux Works or Your Linux Toolbox (for a more playful approach).
But in the end there’s really no substitute for installing Debian on bare metal and tinkering with it. I would really recommend Debian, because it’s the archetype of how Linux systems have been working for the last 30 years or so. Arguably, this is currently changing, but come to grips with Debian before you dabble in more modern approaches to system management.