OS

Graphene OS - The private and secure mobile operating system with Android app compatibility (GitHub)
CalyxOS - Android mobile operating system that puts privacy and security into the hands of everyday users. (GitLab)
Whonix - Whonix™ is software designed to preserve privacy and anonymity by helping users run applications anonymously. Whonix™ can be installed on Windows, macOS, Linux and Qubes. (GitHub)
Qubes OS - Qubes OS is a free and open-source, security-oriented operating system for single-user desktop computing. Qubes OS leverages Xen-based virtualization to allow for the creation and management of isolated compartments called qubes. (GitHub)
TAILS OS - Tails is a portable operating system that protects your privacy and helps you avoid censorship. (GitLab)
nix-bitcoin - a collection of Nix packages and NixOS modules for easily installing full-featured Bitcoin nodes with an emphasis on security (GitHub)