* Runtime problems specific to PGTK build
+** Whether a display server is available cannot be automatically detected.
+
+When started with no arguments from a text terminal and in an
+environment where no display server is specified, Emacs will print:
+
+ $ emacs
+ (emacs:3988): Gtk-WARNING **: 19:19:10.887: cannot open display:
+
+and exit. This is a byproduct of GTK's not providing any means of
+probing for a display connection before committing to opening one, and
+cannot be addressed by Emacs. Rather, users must expressly request a
+text mode session:
+
+ $ emacs -nw
+ [...]
+
** SECONDARY selections don't work on Wayland.
This is because the SECONDARY selection is not implemented by the