Look at the output:
[INFO 00:09:54.255503] [controller:59] Using xim input method.
and
[INFO 00:09:58.726637] [controller:59] Using gtk-im-context-simple input method.
so: I just tried and it works here (so far) with setting GTK_IM_MODULE to an empty string
so just run:
$ GTK_IM_MODULE='' synapse
Look at the output: context- simple input method.
[INFO 00:09:54.255503] [controller:59] Using xim input method.
and
[INFO 00:09:58.726637] [controller:59] Using gtk-im-
so: I just tried and it works here (so far) with setting GTK_IM_MODULE to an empty string
so just run:
$ GTK_IM_MODULE='' synapse