Qt4 is dead and going away. Upstream is aware (see URL) but apparently has not yet found the time to do the port.
Qt5 branch: https://github.com/pstavirs/ostinato/tree/qt5
Qt5 branch was merged to master, but no new release date yet. https://github.com/pstavirs/ostinato/issues/173#issuecomment-387800808
Versions depending on Qt4 were masked.
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=ca35690759de9af60e467999e97a33999e33e574 commit ca35690759de9af60e467999e97a33999e33e574 Author: Andreas Sturmlechner <asturm@gentoo.org> AuthorDate: 2018-07-01 17:00:11 +0000 Commit: Andreas Sturmlechner <asturm@gentoo.org> CommitDate: 2018-08-07 07:27:05 +0000 profiles: Last-rited media-sound/mu{mble,rmur}, net-analyzer/ostinato Closes: https://bugs.gentoo.org/644374 Closes: https://bugs.gentoo.org/656826 Closes: https://bugs.gentoo.org/655382 Package-Manager: Portage-2.3.41, Repoman-2.3.9 media-sound/mumble/Manifest | 1 - .../files/mumble-1.2.4-speech-dispatcher.patch | 49 -------- media-sound/mumble/mumble-1.2.19.ebuild | 122 ------------------- media-sound/murmur/Manifest | 1 - .../files/murmur-1.2.17-ice-3.6.3-compat.patch | 11 -- media-sound/murmur/murmur-1.2.19.ebuild | 130 --------------------- net-analyzer/ostinato/Manifest | 3 - net-analyzer/ostinato/ostinato-0.5.1.ebuild | 25 ---- net-analyzer/ostinato/ostinato-0.8.ebuild | 25 ---- net-analyzer/ostinato/ostinato-0.9.ebuild | 27 ----- profiles/package.mask | 6 - 11 files changed, 400 deletions(-)