Qubes OS is a security-oriented Linux distribution. The main idea of the distribution is "security by isolation" using domains applied like lightweight Xen virtual machines.
Qubes OS is one operating system which gives you the Ability to create different virtual domains to perform different tasks.
So you can go from one domain to another, depending on the task you want to do, while you can also install a completely different operating system.
The latest development snapshot of the project is Qubes OS 4.0.4-rc2 which updates the operating system packages.
"We are pleased to announce the second release candidate of Qubes OS 4.0.4. Qubes OS 4.0.4-rc2 includes many updates from the original version 4.0, namely: All 4.0 dom0 updates to date. Fedora 32 TemplateVM. Debian 10 TemplateVM. Whonix 15 Gateway and Workstation TemplateVMs. Linux kernel 5.4 by default. Error corrections from 4.0.4-rc1.
A point release does not identify a separate, new version of Qubes OS. Instead, it sets the corresponding primary or secondary version (in this case 4.0) including all updates up to a specific point.
The installation of Qubes 4.0 and its complete update leads to the same system as the installation of Qubes 4.0.4. ”
More information can be found at release announcement of the project.