I don't know of any that need some final push. I would think it would be better to just contribute to kde or gnome ui/ux wise. I would say my distro but I almost never click the scroll wheel and just tried it out and it does paste on middle click. No idea why that would be a deal breaker. Also have no idea what windows does on middle click even though its been the majority of what I used day to up until a year or so ago or for the mac even though I used it in the late aughts.

What kind of contributing?

If you mean actually adding code or packaging or testing or anything along those lines, you’re probably looking for gnome. They hate normal linux stuff like middle click paste.

If you mean contributing by using linux, just pick something and start. You’ll have a lot to learn no matter what so there’s no point wasting time trying to figure out what you’re gonna want and working towards that.

If you mean putting other people on linux, don’t do that. It will make them unhappy and cause you lots of stress and work. Find a way to keep them on the systems they’re familiar with, either by using the well documented windows 10 iot ltsc or the accessibility options in macos. People deserve to choose weather or not they switch operating systems and when those decisions are made for them it needs to be done by those who will be working with them every day.

It would be helpful if your example of behaving identical to macos or windows were more clear, since macos and windows behave wildly different from each other. It’s like saying you need a normal european car that works just like your 2500 Silverado or civic si.

OpenSUSE has YaST which allows for more GUI customisation than some other distros. Might be worth seeing if that is what you are interested in.

I see that as full UI/UX behaviour that behaves almost identical to Windows/Mac (is no middle click to paste).

Linux is not Windows. Stop trying to make it work like Windows. Windows is crap and I don't want Linux to work like it.

Expecting Linux to work like Windows is how new people get frustrated. Have you heard anyone say that macOS needs to be like Windows to succeed? Of course not. So stop saying that about Linux.

Also, "no middle-click to paste" is astonishingly stupid, I've been using it hundreds of times per day for way over a decade now. It's one of the most useful and helpful features I've ever used.

Sounds like you are asking for an iPad or a locked down Android pad. The commercial pad offerings to the non-technical public are GUI only, they spend a huge amount of man hours to create the UX. Even if the Linux desktops are getting better every year, you are accepting a limited experience without the terminal.

My experience with ZorinOS has been quite smooth. Though i have opened the terminal for advanced customization and problems with my hardware (nvidia gpu and weird disks configuration), i think there's good chances you don't need it. Although im not very tech savy and i've heard people say that it's not a very good option because they're based on stable but quite old versions of Linux, so i'm just putting the option out here, not saying it's the best

Elementary OS