There have been 3 releases of fractgen since it was added to ports. I've just patched the 2.1.7 release for Qt 5.15.2, but it'd be nice to just catch up with upstream releases. Note that there is a PR (against 2.1.10) specifically for Qt 5.15.2 compatibility, so there's more to do than just update to that release.
^Triage: Reporter is committer, assign accordingly.
A commit references this bug:
Date: Wed Jan 6 00:38:45 UTC 2021
New revision: 560461
Update graphics/fractgen to latest upstream release
The release is a month or two old by now. Some Qt 5.15.2 patches
have landed in the release, but not all of them. New translations
require additional dependencies and patching in the right directory
to search (PREFIX/share).
There are no useful release notes for this release.
Committed an own update and reported the FreeBSD patches upstream.