qjackctl right now is building with hard dependency on X11, for uniqueness checking. Because of this dep, it cannot be started natively on Wayland using "-platform wayland". This could be easily disabled by adding
$(use_enable X xunique)
into the ebuild.The re-emerging qjackctl with USE="-X" fixes segfault in qjackctl.
Also, it seems that it depends on X11:
# Some recent distros (eg. fedora, debian) require this.
This should be also optional, I think, or it should be reflected in the RDEPEND/DEPEND section, at least.