Firstly, once you reach basic competency in Linux, different distributions don't matter. A lot of newbies analyze distros based on what they look like when you install them, often not realizing that it's a pretty simple affair not just to change superficial things like your theme and setup, but entire desktop environments. Basically all distro reviews online are wastes of time for people who know what they're doing. When I came to YouTube, all Linux YouTube was was people constantly installing distro after distro in a virtual machine and critiquing minutiae. It was a bleak and boring world. One of my first and greatest achievements on YouTube was making this video: How to choose a Linux distro: Stop Thinking!, which went semi-viral and sort of put a damper on distro reviews. Either way, I'll say what I think about different distro minutiae here.
Ubuntu is a common distribution because it is the distribution shilled by the company Canonical. Canonical has probably had a positive effect on making GNU/Linux more widely used and accessible, but Ubuntu has a lot of long-term headaches that will plague users.
That said, Ubuntu is nearly the worst distribution for new users. It is maintatined at least, but fails on all the metrics above:
Debian is just a more reasonable version of Ubuntu: it separates free and non-free software clearly—it has a optional version that allows unstable and testing packages for some recent software and it has so few gimmicks it's probably the most boring distro!
I haven't used Debian much as a desktop system (I do use it on my servers), but the package manager and even the release speed of the testing versions isn't quite fast enough for me personally.
Artix is the distribution that I use and have been using for a while. It is really the same thing as Arch, except for Artix allows the usage of different init systems (I use runit).
Arch and Arch-based distributions are "bleeding-edge" in their release time and have access to the Arch User Repository (AUR) allowing the single widest software library of all major Linux distributions.
Artix offers many installable desktop-environment ISOs for newbie users, but thankfully they don't over-bloat them with gimmicky features. Arch itself only has an official minimal installation, and that's kind of its thing.
If I had to choose, Artix is the distribution that I recommend for both novice and most veteran users.
Manjaro is another Arch-based distro. I've even recommened it before for new users in the past and installed it on many people's computers in real life, but I will admit that my view on it is souring. They have definitely started to go the way of Ubuntu by adding lots of extra features, directly people to rely more on flatpak and "harmful" systems and generally adding more layers of abstraction between the user and the system.
All the good things that can be said about Manjaro can also be said of Artix, which also has easy to install ISOs, so I consider Artix the superior system.
Parabola is the FSF-approved, all-free software version of Arch Linux (it also has an OpenRC version for soystemd-haters). In the abstract, Parabola is my optimal distribution, but I don't actually use it anymore for two reasons:
The second problem isn't the end of the world, but it can be annoying.
Gentoo is one of the best distributions and excels in all of the 4 requirements I give. Not only is non-free software obviously separated, but it isn't too difficult to have your Gentoo install with a Linux-libre kernel if you want.
Gentoo is also unique because it is a source-based distribution: you can set basic compilation settings for your programs and have a lot of control over them. While Gentoo is very well maintained, you actually end up with a good bit more control over your system. That is a responsibility that has some prerequisite knowledge of course, so Gentoo has a reputation of being difficult to install.
If you want to look into Gentoo, you should first be familiar with Linux and what specific kind of system you want. When you first install Gentoo, because you can customize it so specifically, it obviously helps to know what exact network backend you're comfortable with, whether you want to use GTK or QT, or many other little things that a Linux noob might not know too much about.
Void is another great distribution.
It's notable also for using runit instead of soystemd, having a musl version, and having a package system reminiscent of Arch, but in many ways more minimalist and extensible.
It again separates free and non-free packages, and has a wide repository of them, included even more installable via the
xbps-src system which is somewhat analogous to the AUR, although unlike the AUR, I don't believe it's quite as easy to update packages.
Void has had a somewhat tumultuous development culture. It was originally the brainchild of one man, one man who went missing for a year... After he returned, drama eventually caused other member of the team to encourage his retirement. Either way, while I used the distro for a while and was one of the first people advertising it online, I never remember this translating into any downstream problems on my computer.
This is only a list of distributions that I've used for a bit. I don't do "distro reviews" or just install random distributions just to test them, so if it isn't here, I'm not going to have an experience-based opinion.