Whonix
Superior Internet Privacy. Whonix can anonymize everything you do online! It runs like an App, is a Free, Open Source and Kicksecure™ hardened Linux distribution.
Tails
Tails is a portable operating system that protects against surveillance and censorship. It's free and you can start it on almost any computer from a USB stick or a DVD.
GrapheneOS
GrapheneOS is a security and privacy focused mobile OS with Android app compatibility. Developed as a non-profit open source project.
Qubes OS
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.