The source project of this merge request has been removed.
List image/avif among supported mimetypes
One user complained that gwenview is able to open AVIF images but not by default. https://www.reddit.com/r/kde/comments/n2ktow/idea_implement_and_endorse_nextgen_image_formats/
We are still missing association between .avif files and gwenview. Adding image/avif to the list should solve that.