Comment 12 for bug 1718719

The Ubuntu diff is
http://launchpadlibrarian.net/334552966/xorg-server_2%3A1.19.3-1ubuntu3_2%3A1.19.3-1ubuntu4.diff.gz

it looks like the backported commits are

xwayland-pointer-confine.diff
+d5e2f271ad93e50 xwayland: Remove two unused proc pointers.
+ca17f3e9fd3b59f xwayland: Lock the pointer if it is confined and has no cursor
+513e3bd3870fdb8 xwayland: Update root window size when desktop size changes
+fafdb0cc9697eb5 xwayland: "Accept" confineTo on InputOnly windows
+c217fcb4c4640ff xwayland: Allow pointer warp on root/None window

xwayland-add-grab-protocol-support.diff
https://cgit.freedesktop.org/xorg/xserver/commit/?id=0a448d133

Ubuntu doesn't have any compositor change, it's standard GNOME 3.24 so there is must be something wrong and it does make a difference without implementing the protocole.

Note that reverting 0a448d133 does fix the issue