Fedora, maybe?

Edit to make my point:

• It is free and open-source.

• Fedora has a rather fast release cycle. It offers new versions roughly every 6 months, along with regular package updates.

• Has been using Wayland by default since Fedora 25, so it aligns with your preference to avoid X11.

• Allows you to set up full-disk encryption.

• Doesn't freeze its regular releases for more than a year.

• Supports a wide variety of hardware and aims to offer the latest kernel and drivers.

• It is a large project.

Notably openSUSE Tumbleweed is a distro that satisfies all requirements while not being named yet by others. Apart from it, only Arch and Fedora are worth mentioning as distros that also satisfy all requirements (as some others have already noted).

NixOS is, if you can cope with a custom "config" language that you will have to use everywhere, your perfect fit.

Updates? Just switch to nixpkgs unstable

No x11? Just don't install it

Encryption? Just use the config options

LTS? If you really want to, just stick to the fixed release channels and have a month of support after next release.

Hardware? Enormous hardware support range, although I don't recommend you run it on a Raspberry pi 3b. (it almost exploded)

Preference towards larger projects? Ooooh yeah its a... gigantic project. And also not to mention nixpkgs is H U G E

Arch.

Maybe EndeavourOS (a convenient installer for Arch) with a desktop that supports Wayland.

I run that with Gnome in Wayland mode on my desktop and with Sway (Wayland equivalent of i3) on my laptop and I've been very happy with that. You could also run KDE if you prefer

NixOS seens to tick all the boxes

Just pull the trigger on Arch.

You've pretty much described Fedora Linux.

It's updates are extremely stable with my record being 15 in-place upgrades without any issues.

I've already written another comment here. But I just noticed that you have edited OP's text to include that you were new to Linux. Which changes the rules of the game so much so that a simple edit of my other post wouldn't do it justice for the sake of visibility. Btw, perhaps you should have told us that earlier 😅.

So previously I had named Arch, Fedora and openSUSE Tumbleweed. These distros are still definitely worth the trouble. However, instead of Arch directly, you might wanna opt to an Arch-based distro. They often come with an installation that's done through a GUI, which you might perhaps conceive as being more intuitive. Though, there are some that argue anything Arch-related is not suited for new users. Personally, I don't buy into that. But there's definitely some truth to it in the sense that other distros might be better suited for some new users. We don't know what 'type of new user' you are, therefore we won't be able to answer that for you. However, my gut feeling tells me that you've got some potential to start out with (an) Arch(-based distro) right out of the gate. Though, I'm not very confident (yet)😅.

With that out of the way, I think the following is important to note as well:

• If you want to avoid X11, then you have to use Wayland. Which, in turn, implies that you've got to use either GNOME or KDE as your desktop environment. Unless, of course, you want to try out a tiling window manager (like Sway or Hyprland etc) right out of the gate as well. Which, again, doesn't make it easier for you to start using Linux 😅. It's definitely worth it eventually, but perhaps it's better to not make it too hard on ourselves from the get-go. Coming back to GNOME and KDE, fortunately they're very well-supported on the previously mentioned three distros. So you should be fine regardless. As to which of the two suits you best...? Well, that's very personal. An oversimplified overview would be that GNOME is polished and 'limited in regards to customization out-of-the-box' while KDE allows you to customize to your heart's content at the cost of polish. GNOME does have support for extensions that allows it to be easily customized beyond what KDE allows one. However, this comes -once again- at the cost of polish 😅. It's best to make your own mind with this. Use both of them, and come to judge them yourself.

• So I can't but notice that you're sensitive to your digital security (which is good thing 👍), but that you'd like your distro of choice to do the heavy lifting; which is totally fair. In that case, I would argue that Fedora and openSUSE Tumbleweed are better suited than Arch(-based distros), because they're distros that take security very seriously. Heck, they're the only popular 'upstream'/'independent' distros that have managed to configure SELinux for use on their distros. On Fedora this is done by default regardless, while on openSUSE Tumbleweed it can be installed at a later point. (IIRC openSUSE Aeon/Kalpa (old MicroOS Desktop) shipped with SELinux by default, but the linked article suggests otherwise 🤔.) In contrast, while you can make it work on Arch, it's not officially supported. AppArmor is still great though*.

• If security is indeed important to you, have you perhaps considered using so-called 'immutable' distros? Btw, the name 'immutable' is not entirely correct as in most cases only some parts (mainly related to base system components) are read-only during runtime; changes to said base system components (through either installing/remove a package or upgrading) happens atomically and often times requires a (soft-)reboot to actually take effect. Some 'immutable' distros even manage to be reproducible and yet some actually manage to be declarative as well. The security-benefits for this can't be overstated. If you're interested in 'immutable' distros, then it's worth mentioning that both Fedora and openSUSE offer them through Silverblue/Kinoite/Sericea and Aeon/Kalpa(/Greybeard) respectively. The exact implementation of 'immutability' across Fedora's and openSUSE's offerings are different. However, I won't go over that for the sake of brevity 😅.

Please feel free to inquire if you so desire!

I think you would get more suitable recommendations if you told us what your use cases are. Did someone else give you those requirements? Are you new to Linux?

Arch, Slackware current (KDE), Suse tumbleweed, Debian sid and Fedora tick all the boxes but I wouldn't recommend Arch nor Slackware to someone who never used Linux before, nor I would recommend Debian sid for desktop usage (unless you know what you're doing) because its packages are not controlled by their security team.

Free and open-source. Receives regular software and kernel updates.

All of them (desktop). The difference in updates is between a rolling release or non-rolling one.
Rolling means they receive updates to software and kernels continuously as soon as they are released, you always have the latest versions but that could lead to instabilities, non-rolling (or stable) are updated less frequently so are more stable, which one to choose depends on what you need to do with it.

Avoids X11.

Fedora, Suse, Ubuntu, Slackware current, Debian, Arch, if you choose GNOME or KDE you'll have Wayland as default AFAIK, probably others.

Supports full-disk encryption during installation. Doesn’t freeze regular releases for more than 1 year.

All of the above.

We recommend against “Long Term Support” or “stable” distro releases for desktop usage.

LTS is a version, not a distro. Distros that offer LTS versions also have a non-LTS ones, get those and you're fine. Tho not wanting a stable is weird, they can be the best for desktop usage depending on what you need to do.

Supports a wide variety of hardware.

That depends on the kernel, all kernels support a wide variety of hardware, non-LTS versions are best for more modern hardware.

Preference towards larger projects.

All distros mentioned are large projects, Debian is probably the biggest, it also supports several different architectures.

Gentoo technically qualifies, but probably isn't what you want for other reasons.

I'd say Archl``inux

Foss

Bleeding edge updates

Only uses X11 if you install it (same for wayland)

Supports disk encryption

Cannot freeze regular releases as there is only one wich get constant updates (rolling release)

As stabel & LTS as you make it

Supports latest harware

Not quite sure what you mean with larger projects but arch is a minimal distro as in you have to install almost everything yourself