@Brian: Thanks for additional info.
I probably tested on Wayland. Now I have tested on Xorg too, and don't
see it there either.
I have one idea (and this is a long shot): Do you possibly have an
~/.XCompose file? If you have, can you try to rename it (in order to
disable it), relogin, and try again. The reason I ask is that I have
<https://launchpad.net/bugs/1849399> in mind. It shows that a mistake in
~/.XCompose might lead to unexpected behavior.
@Osamu: Unloading ibus somehow would only be a workaround, right? I
mean, you should be able to use a Compose key without issues also when
the ibus-daemon is running.
--
Gunnar
