Linux
The Linux Kernel documentation - The Linux Kernel documentation
The Linux Kernel Module Programming Guide
The Linux Programming Interface
GitHub - zen-kernel/zen-kernel: Zen Patched Kernel Sources
Distributions
DistroWatch.com: Put the fun back into computing. Use Linux, BSD.
GitHub - FabioLolix/LinuxTimeline: Linux Distributions Timeline
T2 SDE - The Open System Development Environment
The makers’ choice for sysadmins, developers and desktop users.
Minimalistic
GitHub - EndeavourOS-Community-Editions/sway: EndeavourOS Community Edition setup for sway
Functional
Guix: A most advanced operating system
Embedded
Init systems
runit - a UNIX init scheme with service supervision
upstart - event-based init daemon
System V style init programs - Summary
Package managers
Binary package managers
Snapcraft - Snaps are universal Linux packages
Flatpak-the future of application distribution
Flathub-An app store and build service for Linux