tl;dr: I’m giving up maintaining gnome-directory-thumbnailer as it no longer scratches my itch — it’s yours if you want it.
gnome-directory-thumbnailer is a little project I started a while ago for creating thumbnails for directories (rather than showing a plain directory icon for them in the file manager). Times change, I no longer have the itch that it was developed to scratch, and so I’m giving up maintenance of it after making the 0.1.11 release.
If you use it, or think you should use it, please care about it and take over maintenance. It needs porting to Meson, and some changes to handle working in the brave new world of sandboxed thumbnailers. It’s not a complicated code base to maintain.
If you’re interested, please get in touch, or send a merge request through.