Now ibus-hangul has GSettings configuration in upstream: https://github.com/libhangul/ibus-hangul/commit/1687467cd782077a9b9aa1a0549f6b465efab8c6 I think it's good to test the patch in Fedora with the internal patch.
ibus-hangul-1.5.1-1.fc28 has been submitted as an update to Fedora 28. https://bodhi.fedoraproject.org/updates/FEDORA-2018-add3b2828f
ibus-hangul-1.5.1-1.fc28 has been pushed to the Fedora 28 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2018-add3b2828f
ibus-hangul-1.5.1-1.fc28 has been pushed to the Fedora 28 stable repository. If problems still persist, please make note of it in this bug report.