Ubuntu Linux
Open Source
Desktop OS
Ubuntu is a reliable Linux distribution which is very user-friendly and can be ran on desktops, servers, and IoT devices. Ubuntu uses GNOME as the default desktop environment, but other desktop environments are available.
Notes:
Canonical LTD currently maintains and develops Ubuntu.
Ubuntu also features 10 year security maintenance and CVE Patching for every release. Ubuntu is used by Netflix, Uber, Spotify, Walmart, and many more companies across the globe.
Fedora Workstation
Open Source
Desktop OS
Fedora is a Linux distribution developed by the Fedora Project and sponsored by Red Hat. Fedora Workstation is a secure, reliable, and user-friendly edition developed for desktops and laptops.
Notes:
Fedora by default comes with the GNOME desktop environment, but other desktop environments are also available.
Aside from just being a desktop OS, Fedora also provides a server edition, called Fedora Server.
GrapheneOS
Open Source
Mobile OS
GrapheneOS (formerly known as CopperheadOS) is a free and open-source security-focused mobile operating system built on top of the Android Open Source Project. It currently specifically targets devices offering strong hardware security.
Notes:
GrapheneOS is also hard at work on filling in gaps from not bundling Google apps and services into the OS.
Hundreds of strong privacy & security enhancing features are also included in GrapheneOS. You can see the full list here -> https://grapheneos.org/features