I think it its replacement is dev-perl/Digest-SHA
Nah, the alternative is shipped in perl itself, as indicated by virtual/perl-Digest-SHA And we still have a raft of things that need Digest-SHA1 ( and its not entirely straight forward to replace one with the other ) https://qa-reports.gentoo.org/output/genrdeps/dindex/dev-perl/Digest-SHA1 I'm not even really sure about the motives for using one over the other, as some of the newer projects in that list (Rex) use Digest-SHA1 So more investigation is warranted, but ultimately, these changes should be made upstream if at all.
Not a Gentoo problem.