Linux

There was another post yesterday about this and the community recommended Mint & Pop OS the most. However, I am not looking for windows-like. I want a new & fresh experience like using a smartphone for the first time or switching from ios to android.

While I get why Linux Mint (with the Cinnamon DE) is regarded as a Windows-like, Pop!_OS is far from that. Furthermore, going from iOS to Android is arguably a smaller change than going from Windows to any Linux DE (so even the Cinnamon DE (on any distro)). Regardless, the Desktop Environment is the single most influential part of a distro to how you experience any distro. Therefore, if you actually want a new & fresh experience, then you should definitely check out DEs like Cinnamon, GNOME, KDE Plasma and Xfce^[1]^ on something like a Live USB (perhaps through the use of Ventoy). After you've experienced a bunch of DEs, you should have attained a better grasp of what you like and don't like.

Distrochooser.de recommended kubuntu to me.

While Distrochooser is cool and all, you shouldn't take it too seriously 😅. If possible, consider sharing your results on Distrochooser, that might at least provide us some pointers.

1. Too many to list actually 😅, and most of them shouldn't be of a concern to a new user (or have simply become mainstays on most distros). The most important 'block' would be the Desktop Environment, though. Furthermore, design choices like release model, independent/derivative, opinionated/blank slate, traditional/atomic etc and a distro's popularity are other important factors in making a decision; while we'd refer to none of them as "building blocks of a distro". However, if there are any "blocks" that you would describe as a hard-requirement for you, then it does make sense to look for a distro that meets those. For example, in my case; a configured SELinux and atomic upgrades^[2]^ are required. As such, the decision already boils down to like two distros 😅. The shopping experience approach would perhaps make more sense if you chose a distro with little to no defaults (à la Arch (or Gentoo^[3]^)). Finally, perhaps it's worth noting that ((Dynamic) Tiling) Window Managers' capability of leaving you in awe for the opportunities and possibilities they provide are more substantial. Thankfully, while not as feature-rich, the more established DEs do offer means to engage with (dynamic) tiling (through extensions/add-ons).
2. That's hard to find; obviously distros won't advertise what they're missing. Heck, I wouldn't be surprised if they have good reasons for their respective design choices. Still, FWIW, resources like these might be helpful to some. However, you should only look at the tables, the texts found above the tables are at best outdated and perhaps even misleading otherwise. Beyond that, if you narrow the choice between just a couple of distros, then I'm sure the community would be more than willing to point you toward their differences.
3. Software I would recommend to anyone would be:
   • Distrobox; this excellent piece of software has single-handedly solved package availability across the Linux landscape. Other excellent endeavors like AppImage, Flatpak, Nix and Snap definitely have their uses and are in some aspects superior; but Distrobox' ease of use (contrary to Nix) and (almost) boundless access to packages (contrary to AppImage, Flatpak and Snap) on top of how well it integrates with the rest of your system makes it my personal MVP.
   • Flatseal; must-have if you ever plan on using flatpaks (which you definitely should consider).
4. It depends entirely on the distro you install. Assuming that you start using a distro with sane defaults (like most new users do), then unless you're using an Nvidia GPU^[4]^ (or other hardware known for causing troubles), you can start using your system however you'd like it; which for most would consist of installing the software they need. Furthermore, concerns related to bloat are a lot less significant/severe on Linux, so you should be fine unless you think the default installed file manager is bloat...
5. I actually don't know. Perhaps it might be related to creating an as homogeneous experience as possible; apps on Linux either rely on GTK or QT for their appearance/looks etc. Therefore, by foregoing one, the 'awkward' 'out-of-place'-experience that some might experience every so often would have been overcome. But this is a rare concern (I'd say). So unless you're very into how your system looks and feels, it shouldn't be a concern to you.
6. I think these questions show that you've put some thought into this and that by itself is already very commendable. And I'm actually of the opinion that asking these questions, especially for someone like you, is important. So I would definitely encourage you to continue with asking relevant questions in hopes of making the transition to Linux as pleasant as possible. As for the distros you've mentioned, chances are high that you'd be content with either one of them. However, I wonder if you're making a conscious choice; like would you be able to state why any of these should be preferred on the basis of merit rather than popular vote^[5]^ or what happened to come out of Distrochooser.

1. Important distinction: these aren't selected for how different they operate/behave compared to Windows(/macOS) but for being some of the more polished DEs found on Linux. For a more exhaustive list, refer to the one found on the ArchWiki; which still happens to miss DEs like Kera 😅.
2. I wouldn't call atomic upgrades a building block as it's ultimately a design choice.
3. Gentoo is a great distro, but I would not recommend a new user to engage with it; unless you believe you belong to the sub 1% that can make it work as their first distro. Heck, even Arch is often discouraged to new users. Though I think that Arch might be just up your alley; at least if you enjoy reading the excellent ArchWiki.
4. In which case, either the installer provided by the distro got your back and the proprietary drivers are installed or you're required to install them yourself. Steps related to these are different per distro, but reading up on your chosen distro's documentation should be sufficient.
5. Don't get me wrong; I'm not dismissing the popular vote.