I have some problems with X11 cursors and that's quite normal with Wayland obviously

It's not. There is no Wayland specific cursor format, it's all just images on disk, and the most widely used format hasn't changed away from Xcursors yet.

For example, my cursor can become invisible if my screen sleeps

That's either a compositor or driver bug, please report it (as I've never seen that on Plasma, to your compositor first).

Additional controllers that control mouse cursor don't control X11 cursor, however they still work, I just don't know where the cursor is unless it highlights something.

That's because it moves the X11 pointer but not the real one. A cursor theme can't change that.

In the case of one project in paticular, that being the Sunshine game streaming project

That's a terrible example, because they completely ignore the many many years old standardized APIs (screen casting and remote desktop portals) that they could use, in favor of doing hacky and broken things that require root access instead.

Xwayland doesn't get input in some special way, it uses the exact same Wayland protocols to get input events as native Wayland apps. All claims about it being more complete or anything like that are nonsense.

Krita forces Xwayland because they have some X11 specific code they haven't bothered porting away from, that's all.

To maybe prevent a catastrophe: The system is not able to restore virtual desktop assignments yet, it only starts the apps you had open before.

S3 is standby. Hibernate is S4

It's been possible for a long time, but yes, now you can do it intuitively in the shortcuts GUI

Most displays provide settings to modify the colors of your screen; mine has like 10 different "picture modes" that strongly modify gamma curves, colors and the whitepoint. The EDID only describes colors of one of them, so if you change display settings, the data no longer applies.

More generally, the information isn't used by Windows or other popular video sources by default, so manufacturers don't have much of an incentive to put correct information in there. If it doesn't make a difference for the user, why would they care? Some displays even go so far as to intentionally report wrong physical size information, to make Windows select the default scale the manufacturer wants to have on that display (or at least that's what I think is the case with my cheap AliExpress portable monitor)...

That's not to say that the information is actually often completely wrong or unusable, but if one in tenthousand displays gets really messed up colors because we toggle this setting on by default, it's not worth it. We might add some heuristics for detecting at least usable color information and change this decision at some point though

I was especially surprised to find that Gnome would turn the screen around correctly by itself. With KDE Plasma I had to set the correct screen orientation myself. And unfortunately Plasma also did not come with any on screen keyboard so it was effectively unusable.

You just need to use a distro that follows our upstream defaults - namely Wayland, and having the virtual keyboard Maliit installed by default - then everything will work out of the box with KDE Plasma too.

Thst might change with Flathub's ambitions to become an actual app store though

No. Source 2 still uses some X11 specific stuff and has to be ported over to Wayland before it can work Wayland-native

Professionals call it a "layer 8 problem"

Another issue I have is that my touchpad doesn’t get detected if I’m holding down a key

That's a libinput feature, meant to prevent you from accidentally using the touchpad when you're typing. You can disable it if you want.