NixOS, Guix System, SerpentOS, Bedrock and T2 Linux? Meta-distributions (could be either simple config-based reproducible systems, immutable atomic distros or functional transitive-dependency package managers), micro-kernels and distributed systems are the next cool, bleeding-edge stuff in FLOSS OSes, and most of those projects are still in development.

By the way, NixOS and Guix System use Stores, instead of FHS (File Hierarchy Standard). To take it up one notch, Guix uses shepherd instead of systemd, so if anyone over here dislikes Lenning or systemd for some irrational reasons, you've got a nice distro, I guess. But do note that you don't get to swap init systems in both NixOS and Guix System - you're stuck with systemd and shepherd respectively.

Alpine Linux, because it uses OpenRC and musl, it's an interesting choice a little bit different but I really like it nyself for servers.

Gentoo, the biggest source based distro, has Emerge, a very configurable package manager.

NixOS, uses the Nix programming language to install packages and configuring the system. Very powerful and breaks many conventions about Linux systems

You could try a rolling distro like OpenSuse Tumbleweed, or something from the Arch lineage (Arch, Endeavour, Garuda, Manjaro in order from less to more handholding).

You could also try something from the Red Hat rather than Debian world,.for example Fedora has several interesting editions, there's the WorkStation desktop edition and Silverblue which uses Android immutable principles.

I'm pretty comftable with linux mint right now

For the love of God, spare your free time and don't move from what works. Consider tweaking your system instead and moving only when you broke something

If you don't mind reading a little bit and "work hard" to get some things done and "have fun" then I'd suggest to try :

• NixOS (it can do magic!)
• Arch Linux (easiest is the Arch based EndeavourOS and the shiny colorful Garuda Linux), learn some pacman and AUR.

Linux from scratch, does that count?

(It isn't a distro, but more of a learning project that will expand your knowledge a lot, after you've emitted buckets of blood, sweat and tears)

I'm a huge proponent of Gentoo Linux as a learning experience. It's a great way to learn how the components of a system work together and the distro enables an amazing amount of configurability for your system.

Even following a handbook install in a VM can be a good experience if you're interested.

I've been on an immutable distro and declaritive distro kick lately.

So the bluefin project, which has so much sugar it a damn cake (in a good way, lots of stuff to get you to a usable running state for a lot of Dev environment and gaming).

I'm digging into SUSE microos more now, mostly to play with elemental (I really want a featureful CI/CD env for my desktop, so containers to full VM and isos is neat to me).

Nix has been super, super useful for packages that I want between OSs, but the alure of getting better configuration with them on full nixos is slowly drawing me in.

Guix on the other hand is my current ideal, I am just super impressed with their full source bootstrapping and really love a lot of the philosophy of the project, but they don't get as much love from the professional crowd (nonacademic, non amateur).

Nixos is a declarative distro, it's an interesting concept.

Also, Immutable distros:

• Fedora Universal Blue
• Bazzite OS
• Vanilla OS
• Blend OS

Install virtual manager (sudo apt install virt-manager)

From there you can spin up as many VMs are you desire as long as you have enough ram. I like Fedora