Distributions
Choosing a distribution can be challenging! (Though it actually matters less than you think.)
Here's a short and incomplete list to help you choose:
Debian-based (easiest):
MX Linux
Mint
Ubuntu
Debian
Pop! OS
Elementary OS
Zorin OS
Kali (for hackers)
Arch-based (harder):
EndeavourOS
Manjaro
Garuda
Arch (hard)
Artix
Red Hat based:
Fedora
Red Hat (usually used on servers, including the UCLA lnxsrvs)
CentOS (Red Hat but without the tech support)
Other:
OpenSUSE
Void Linux
Gentoo (hard)
Not Linux:
OpenBSD
FreeBSD (we run this on some of our servers)
Tips for selecting a distro
If you are a beginner and you don't want to mess with the terminal that much, choose a Debian based one like Mint. Most of the Debian ones just work straight out of the box. There's also tons of support.
If you have some experience (or you're a beginner who is fine with using the terminal), you can try one of the Arch-based distributions. Installing Arch takes a while, but it's actually not too hard. If you're too lazy to install Arch, choose a distribution with a graphical installer (like EndeavourOS).
Here's a quiz you can try: https://distrochooser.de/en/