GNOME has kind of always been on the opposite end of the configurability spectrum from KDE, IME.

But also I'm not super clear on how libinput fits into the picture, I think there used to be some Synaptics-specific integration in certain places that I never went back to, to confirm the differences (switched to libinput several years before, and I've completely forgotten since what I was trying to solve back then).

Anyway, I ended up writing a mostly-personal-anecdote below, that would likely not help, so you can probably skip it (if you do want to try anything, KUbuntu and https://neon.kde.org are both on top of Ubuntu, and there's other distros, but I've not kept up with any distro I might recommend)

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I tried Ubuntu (w/ the GNOME default) once (back in KDE 4 times IIRC) and the lack of almost any flexibility felt like I was stuck in a sandbox (a literal one, like from when we were kids, not that it's easy to remember that far back).

The only other time I felt like that was when a friend gave me their old iPhone (6 IIRC?) "to see what it's like" and I had to give up trying it out because both the OS, and the few apps I could find (for its max supported iOS version), had random chunks of features missing (tbh I should've jailbroken it, then it'd just be one more piece of hardware I have no immediate use for - but I digress)

KDE is far from perfect (switched to Wayland recently, and been tracking a few QoL leaps in the next couple releases), but I can at least try to tweak it - same goes for using NixOS or ZFS tbh (not going to even defend those, but I have done both Gentoo-like shenanigans, and randomly RAIDed a dual-SSD laptop, respectively, quite painlessly despite not preparing for it from the start, and the weirdness budget is personally paid for a thousandfold).

Meanwhile I run into e.g. GNOME apps using libadwaita nowadays needing environment variables (that appear deprecated?) to apply the KDE gtk integration theme so they don't stick out like a desaturated winamp skin.

I've never felt like "power user" applied well to myself, like I'm not doing the equivalent of weight-lifting for computers, never want to be doing sysadmin if I can avoid it, I just want to have enough control to make things seamlessly neat for myself.

Opinionated defaults are great in the same way you'd set up a house for a marketing reel, but if I actually buy it, why would I have to deal with a landlord telling me I can't paint the walls or move/replace some furniture to maximize my comfort?

The "personal" in "personal computing" is supposed to be the same as the one in "personal property", and so I'd have similar expectations of "can screw with it without asking for permision" for both (modulo real estate being seen as an investment, and building codes, etc. - should've picked a smaller example than a house, oh well).

To stretch the house analogy further, just like I have leased (some corporation's) private property as office spaces, I would be fine to doing the same (also for business reasons) with e.g. a cloud platform (most likely through GHA, whenever they announce the paid tiers) - tho be fair to everyone, this applies far more to walled gardens than opensource software like GNOME.

Also, to be clear about the "sandbox" thing: sandboxes (and/or ideally more objcap systems) are great, and I think that the XDG Portal work is incredible for what it allows: the apps are getting sandboxed, the user getting more power over them.

Even without Flatpak (which I keep meaning to try out), I was happy to see e.g. the KDE Wayland screenshare dialog outright has an option for "create virtual screen" (which can further be configured in the KDE settings, and e.g. partially overlapped with a physical monitor, etc.).
If the app was in charge, they would barely enumerate some of the windows correctly, let alone provide new virtual screens.