Hello,

today I installed KDE neon (User Edition). It looks very nice, installation went without problems, everything looks professional.

My only problem was that gwenview refused to open my images in AVIF format and thumbnails in dolphin were not shown.

I investigated the problem and observed that image/avif mime type was not installed, because of old shared-mime-info package version 1.15, latest version is 2.1 (AVIF mime type was added to 2.0).

When I registered the mime type manually everything was perfect.

I'd like to suggest/recommend to upgrade the shared-mime-info but I don't know whom to contact.

Since Neon uses Ubuntu 20.04, and they provide said package, Neon doesn't handle this

However:
just install libavif-bin. Then, thumbs and gwenview will work with these files. It adds the missing support as well as the mime info.
Neon build this themselves, as it is not available in Ubuntu until 21.04.