Remove onboard dependency due to Wayland migration

[meisenzahl]

Problem

With our recent transition from X to a default Wayland session, the onboard package has become obsolete as it is not functional under Wayland.

In addition, onboard is no longer packaged for other distributions such as Fedora 40.

Proposal

Remove onboard as a dependency from the project, as it no longer serves its purpose in our new environment.

Consider alternative solutions for an on-screen keyboard:

• Further develop elementary/keyboard: We could continue improving this project to support our Wayland session.
• Integrate an on-screen keyboard into elementary/gala: Alternatively, would it make sense to integrate this functionality directly into Gala? This could streamline the user experience by having a built-in solution within our window manager.

Prior Art (Optional)

No response

[meisenzahl]

@tintou do you have any insight into whether elementary/keyboard could be adapted to work under Wayland? Thanks in advance for your thoughts!

[danirabbit]

Another alternative is https://github.com/droidian/squeekboard

[tintou]

Another alternative is https://github.com/droidian/squeekboard

Mutter doesn't support layer-shell, virtual-keyboard-v1 nor input-method-v2 protocols so this won't work without significant effort

[meisenzahl]

@tintou can you estimate whether the implementation effort would be reduced if we would implement the keyboard directly in Gala?