SUMMARY Today I found out (downloading images) .AVIF is a new (2019) image/video format meeting International Standards Organization (ISO) and other specifications, and has better compression than most/all other formats, so should KDE support it for things like file managers & image viewers (or general library that would work for all)? STEPS TO REPRODUCE 1. Try to view/open an .AVIF in a file manager or image viewer/editor. OBSERVED RESULT .AVIF seems currently unsupported. EXPECTED RESULT Consider programming .AVIF support. SOFTWARE/OS VERSIONS UNIX/GNU/Linux/KDE Plasma: FreeBSD UNIX 13.1, Slackware64 15+current & KDE Neon 20.04 GNU/Linuxes KDE Plasma Version: 5.26.2 KDE Frameworks Version: 5.99.0 Qt Version: 5.15.6 ADDITIONAL INFORMATION X11. I can later possibly also test NetBSD, maybe DragonFlyBSD.
Have you installed kimageformats?
Slackware: kimageformats-5.99.0-x86_64-1 Neon: updated this month, but forgot how to check package
Make sure you have kimageformats installed and that your distro enables libavif support for it.