$ sudo dnf install libheif-tools
For RAW support:
$ sudo dnf install rawthumbnailer
This automatically had support for CR2 Canon and ORF Olympus files I have. But it was not supporting Fujifilm RAF.
/usr/share/thumbnailers/raw.thumbnailer I could see that RAF was not included as a recognized mimetype.
Luckily, all it took was adding:
And voila, Gnome began showing thumbnails for RAF!