Qt4 is dead and going away.
Someone has put work into a port to Qt5 (see URL), but it is not upstream yet.
Created attachment 531858 [details, diff]
661 version bump with Qt5 patch.
Note that the patch is too big for $FILESDIR so needs to be hosted.
The bug has been referenced in the following commit(s):
Author: Andreas Sturmlechner <email@example.com>
AuthorDate: 2018-05-29 13:41:36 +0000
Commit: Andreas Sturmlechner <firstname.lastname@example.org>
CommitDate: 2018-05-29 13:41:36 +0000
sys-boot/unetbootin: 661 version bump w/ Qt5 patch
Disabling FTP sources.
See also: https://github.com/unetbootin/unetbootin/pull/137
Package-Manager: Portage-2.3.36, Repoman-2.3.9
sys-boot/unetbootin/Manifest | 2 +
sys-boot/unetbootin/unetbootin-661.ebuild | 97 +++++++++++++++++++++++++++++++
2 files changed, 99 insertions(+)