Matthias Clasen, Fedora Desktop Team Leader, member of the GNOME Release Team, and one of the active GTK developers (contributed 36.8% of the changes in GTK 4), began discussing the possibility of deprecating the X11 protocol in the next significant branch of GTK5 and leaving the ability to run GTK in Linux only using the Wayland protocol.
A note to the X11 deprecation proposal states that "X11 isn't getting any better, and Wayland is already ubiquitous." It further explains that the X11 GTK backend and Xlib-based code are stagnating and experiencing issues with maintainers. It is stated that in order for X11 support to survive, someone has to write and maintain X11 related code, but there are no enthusiasts, and the current GTK developers are mainly focused on Wayland support. System developers interested in working in environments based on the X11 protocol can take the maintenance into their own hands and extend its support in GTK, but given the current activity, the scenario that there are those willing to take over the maintenance of the X11 backend is considered unlikely.
Currently, GTK is already positioning Wayland as the main platform for developing functionality and APIs. Due to the lack of any activity on the development of the X11 protocol, while leaving its support in GTK, the X11 backend will lead to an increasing backlog in terms of new functionality available to developers, or will become an obstacle to the implementation of new features in GTK.
Source: opennet.ru