I am having trouble with the shotcut version in the repos not showing the previw. I don't have this problem on 24.09.13 which I downloaded from the shotcut website. I've created a PR but is was rejected.
As the requested shotcut 24.09.13 version includes media-libs/mlt 7.28.0 upstream (https://www.shotcut.org/blog/new-release-240913/) I also created bug #939775 which is a mlt version bump.