At least for KDE Plasma, we've had accessibility features added in Plasma Wayland every release since 6.0.
- 6.0: colorblindness filters, shake cursor
- 6.1: bounce keys
- 6.2: visual system bell, sticky keys
- 6.3: pixel perfect magnification
- Upcoming in 6.4: mouse keys, Orca 48 a11y keybinding support (so far)
We've made it a central part of KDE development and much of this has been leveraging capabilities that are only available in Plasma Wayland to do correctly.