media-gfx/digikam-5.3.0-r1 crashes reproducibly here when trying to fix red eyes. I was able to reproduce the problem also using the 5.3.0 appImage. The bug was already reported upstream: https://bugs.kde.org/show_bug.cgi?id=372831 A patch was also published (see comment #2, https://bugs.kde.org/show_bug.cgi?id=372831#c2). I applied the patch here and it indeed fixed the problem. As version 5.4.0 is not even in the tree yet (see https://bugs.gentoo.org/show_bug.cgi?id=605800) it might be a good idea to apply the patch to the current Gentoo version. For me fixing red eyes is a basic feature when processing images.
Thanks, fixed in digikam-5.3.0-r2.