Nomacs stopped understanding AVIF after update

[tkzv]

I use media-gfx/nomacs to view images. After the last update it stopped opening AVIF format. media-libs/libavif is present.

As far as I understand, Nomacs uses Qt libraries to read most formats. Back when GwenView and Nomacs both used Qt 5, both read AVIF. After the world update GwenView uses Qt 6 and opens AVIF, but Nomacs uses Qt 5 and doesn't open AVIF. Looks like some Qt 5 library was rebuilt without libavif support. How do I find what went wrong?

Judging from kde-frameworks/kimageformats description, it seems to be what provides additional image plugins for Qt. It was updated from 5 to 6. If this is correct, how do I find the Qt package, which needs USE flags changed to pull kde-frameworks/kimageformats?

UPDATE: Yes, installing kde-frameworks/kimageformats:5 fixed the problem. But the question remains: what flags for what package do I need to change to make this permanent? Or how do I create a virtual package, that pulls kde-frameworks/kimageformats:5 as long as media-gfx/nomacs depends on Qt 5?