linux handbook - Robuta Search

https://linuxhandbook.com/

An independent, reader-supported publication focusing on Linux Command Line, Server, Self-hosting, DevOps and Cloud Learning

https://modern-linux.info/

A Handbook for the Cloud Native Practitioner

https://www.opennet.ru/links/info/619.shtml

https://linuxhandbook.com/member-resources/

You get exclusive benefits for being a sudo or root member of Linux Handbook. Here are the ebooks available for free to the pro members.

https://shop.linuxnewmedia.com/shop/dia0025-raspberry-pi-handbook-special-edition-25-digital-issue-139?category=21