sudo emerge -av kde-apps/okular

These are the packages that would be merged, in order:

Calculating dependencies... done!

emerge: there are no ebuilds to satisfy "media-libs/imath:=".
(dependency required by "kde-frameworks/kimageformats-5.85.0::kde-kit[openexr]" [ebuild])
(dependency required by "kde-apps/okular-21.08.1::kde-kit[image-backend]" [ebuild])
(dependency required by "kde-apps/okular" [argument])

This was, of course, immediately after an ego sync. There is indeed no media-libs/imath ebuild in the tree.

sudo emerge -s media-libs/imath

[ Results for search key : media-libs/imath ]
Searching...

[ Applications found : 0 ]