could it be that the solution you found, had been somehow related to Ubuntu? In TDF released rpm packages there is no libreoffice-gtk3 package and thus you won’t find it anywhere. The functionality is (most probably you are looking for the VCL GTK3 plugin) in package
libobasis6.3-gnome-integration-188.8.131.52-2.x86_64.rpm (esp.: shared library
Hope that helps.
Incidental remark People answering questions on this site are in general not affiliated in any way with TDF but users like you. Thus don’t assume by using phrases like your version, your software or similiar ones, you are talking with some kind of representatives of a (non-existing) vendor of LibreOffice.
If the answer helped you to solve your problem, please click the check mark () next to the answer.