If there are Qt 5 image plugins installed, Nomacs detects and uses them. The package that provides those plugins is kde-frameworks/kimageformats:5. I suggest adding to media-gfx/nomacs ebuild an extra USE flag, that will pull kde-frameworks/kimageformats:5 when enabled. Alternatively, there can be flags 'avif' 'eps' 'heif' 'jpegxl' 'openexr' 'raw' each of which would pull kde-frameworks/kimageformats:5 with the corresponding flag. Reproducible: Always