Its closed because the OP reported it [working](https://github.com/geany/geany/issues/2079#issuecomment-460280724).
That a further problem has been discovered probably would have been better as a new report.
There are a number of reports of Wayland/XWayland issues with many programs, basically xwayland isn't X11 and doesn't work the same, so apps written for X11 like GTK seem to have problems with xwayland.
Since none of the devs have a suitable setup (AFAIK) you will need to provide more information, starting with running Geany as a Wayland app, as Xwayland and (if possible with proper X11).