It doesn't open with a summary or overview but dives right in to exploration, but I think the point comes across:

The copy and paste key codes, which have no physical keys anymore, are - to a degree - supported in software. Their claim is that those key codes are the tool for universal copy and paste, and then it's the input interpretations job (key and combination mapping) to offer bindings to those key codes.

GTK added support the copy and paste keyboards in January 2025. QT also added support for copy and paste key codes the same month. I'm not sure of the first released version of the GTK toolkit that will contain the fix. For QT, it will be QT 6.10, scheduled for release in September 2025. Together, this will cover many apps built for Gnome and KDE as well as others that use the same toolkits.

… followed by some more "current state of support for those key codes".