This MR breaks winewayland's support (or to be more accurate emulation) of pbuffers, see https://gitlab.winehq.org/wine/wine/-/merge_requests/6298. Is this planned to be reintroduced later in win32u? I think something along what's described below could be implemented in win32u as a generic pbuffer emulation strategy when the backend doesn't advertise any pbuffer capable formats.
In short, Wayland EGL doesn't support pbuffers, so previously winewayland emulated them through: 1. Backing WGL pbuffers with EGL window surfaces with an offscreen/dummy (i.e., not given any role) Wayland surface. 2. Marking all formats as pbuffer capable, and, additionally, since pbuffers are usually requested as single-buffered, we advertised single-buffered, pbuffer-only variations of all the formats (I think this latter feature was dropped already in some previous MR).