Gentoo's Bugzilla –
Attachment 768644 Details for
Bug 836726*/* revdeps with BDEPEND=dev-qt/qthelp are queued to update beforehand, then broken by qhelpgenerator: "Cannot mix incompatible Qt library (5.15.3) with this library (5.15.4)" (e.g. KF5Libkleo.qch not found)