Linux Server
As already stated, I recommend Alma Linux (a Red Hat Enterprise Linux fork). Spin up another virtual machine and install Alma Linux 8.7 for running through Linux administration tasks. Later, this will be an AWS EC2 instance, but it's always nice to have local servers for experimentation.
Red Hat Enterprise Linux 9.1 is generally available at the time of writing, but from my impression, there are still a few bugs that need ironing out. Later, I'll validate the information here, but I expect it to be the same.
Download the minimal ISO: https://almalinux.org/
There are still a few Red Hat Enterprise Linux specific sections such as on Subscription Manager for example.
The following section serve as a quick reference to the most common system administration tasks.