The following is just my opinion. Opinions will vary. There seems to be a little passive/aggressiveness on this subject.
For the most part, no one wants to come out and just say brandX is the best one. But then, everyone kind of does it anyway. I can tell you which distro most of the people on this website will recommend, simply by comments they've made over the last couple of years. I'm as guilty as anyone. Having said that, I will do my best to keep this generic.
This is a little like asking what's the best vehicle for me? A motorcycle, a subcompact, a pickup truck, an SUV, or a semi tractor-trailer.
It kind of depends on what you want it to do.
Ubuntu, Mint, Fedora and openSuSE all have reputations for being user friendly and easy to install.If you're a beginner, I would likely start with one of those.
Kali and NST are more pen testing/hacker based, if you're a beginner, I would stay away from these. We probably get more questions about how to do simple things in Kali than any other distro. The video driver doesn't work, the wi-fi doesn't work, I can't compile this thing. Most of these questions are thing experienced users know how to do pretty easily. If you're a newbie beginner, I highly recommend you stay away from Kali Linux.
If you're primaily interested in servers, cloud VMs, and data center Linux's, I would go with Redhat, CentOS, AlmaLinux, RockyLinux, or EuroLinux. Most of these are based on Redhat, which is itself based on Fedora. These Linux distro's have a lot of enterprise tools not available in some distro's, and not installed by default in other distro's. Depending on which website statistics you believe, Redhat and it's clones own over 75% of the data centers
and cloud back-ends.
If you're primarily interested in the "latest and greatest" newer Linux stuff, I would go with Arch or Fedora. They tend to be more "up to date", but less thoroughly tested than other distro's. The nice thing about these distros is they get the newest drivers for video, wi-fi and sound cards before everyone else.
My personal opninion of Arch, is that it's not for beginners. It is one of the most difficult to install distros, and pacman is probably the least intutitive package manager in existance.
If desktop GUI innovations are your primary interest, I would go with Ubuntu or Mint.
If Linux system inoovations are your primary interest, and the future of Linux is a concern, I would go with Fedora, they were first with most of the common sytem practices, wayland, network-manager, systemd, podman, pipewire, etc...
If the number of vendor supported packages is important to you, then Ubuntu, Mint and Fedora are definitely the way to go. They literally have thousands more packages available than just about everyone else. There are some 3rd party packages that will only install on Ubuntu or Rehat/Fedora. That's not to say you can't get them working on other distros, it's just a lot more work, and a lot of manual intervention is required.
If you are into "roll your own". I would start with either Ubuntu or Fedora, as they have the best development tools available.
Then start with LFS ( Linux from scratch ) and go through the exercise of building your own custom version of Linux. Then you'll have a good idea of how much it is to build and maintain a distro and all the packages associated with it.
If documentation is important to you, Redhat, openSuSE, SLESsuse, Ubuntu and Fedora are all very well documented, head and shoulders above almost everyone else.
If security is a big concern, Redhat is what the US government, the military and the RSA use. At a more consumer grade level Qubes, Tails, and Alpine are pretty good.
But keep in mind, you can "harden" just about any Linux distro. There are some vendors that specialize in this and sell "pre-hardened" Linux images.
If getting back to Linux roots in important to you, Debian is probably the closest to what Linus originally wrote, but I understand he uses Fedora these days.
If stability is important to you, go with what is called an LTS version of Linux. These typically use older kernels and older libraries, that are more tested over a year or two before they are released. Redhat and it's clones are probaly the most stable, and have the most enterprise tools like clustering, NIC teaming and bonding, they are made to be resilient and very stable. Redhat's highest priority is uptime for systems. Ubuntu and Debian are also gaining ground in the Linux server market.
If you like being different from the crowd, a few good distro's I have used that are less popular and less mainstream would be PuppyLinux, MX Linux, Parrot Linux, Easy OS, and Mandriva. In the end, it's hard to go wrong, most of them are all good. Again, it depends on what you want to do. If you more of a traditionalist and like the way "Linux has always done it in the past". There are some distros that still avoid systemd, networkManager, and wayland.
AT&T, Tmobile, Chase Bank, and US Bank are all Redhat Shops. Amazon Cloud runs mostly on "Amazon Linux" which really Fedora. Azure cloud runs on Windows Servers.
Google cloud and Oracle run on OracleLinux, which is a Redhat clone.
Ubuntu is support by Canonical which has a lot of partnerships and ties to Microsoft.
Redhat is owned by IBM. A European group called EQT owns SuSE Linux. It's interesting to note that SuSE is the most popular distro in Europe.
As much as I hate "supporting the man" and corporate distros, the truth is, they have best support, best documentation, and most packages. One of the reason Linux exists, was the get away from commercial OS's like MacOS and Windows. There are plenty of distros that do a good job of avoiding corporate sponsorship, there is a balance here with some distros. RockyLinux is a good example, it's 100% community based, has no corporate sponsorship, but is 100% based on
Redhat.
https://www.distowatch.com reports over a 100 active Linux distributions. In reality, most of these could be tied back their parents.
Debian, Fedora, Arch, and SuSE. The background screen and logos might be different, the default packages installed might be slightly different, but for the most they are the same.
For the record, BSD is not Linux. All the derivitives, such as FreeBSD, NetBSD, OpenBSD, are a lot like Linux, but it's a different kernel, and while many of the commands are the same as in Linux, many are not. Generally it's closer to "real" UNIX.
The UNIX flavors are BSD, HPUX, AIX, and Solaris, there are a couple more I can't remember the names of right now.
MX, Parrot and Ubuntu are based on Debian.
Redhat and all it's clones ( AlmaLinux, RockyLinux, CentOS, OracleLinux, etc.. ) are based on Fedora.
Mint is based on Debian or Ubuntu.
SuSE(SLES) is based on openSuSE.
EndevorOS is based on Arch.
Gentoo is pretty much a stand alone distro that doesn't copy anyone else.
This is by no means a complete list, but hopefully it will give you an idea of how all this ties together.
This is a touchy subject, there are sites like...
https://danielvintner.com/blog/tree-of-linux
That seem to infer all Linux is based off Debian, but many distro's are not. If you google "Redhat family tree" you'll see an entirely different list.
www.silabs.com
