How to understand: nautilus not generating _any_ thumbnails on SMB shares

I need some help understanding how the thumbnail process works with Gnome Nautilus. I am running Gnome 43.2 with nautilus 43.1 on Manjaro Linux.

Other computers show file thumbnails just fine on my home server (debian) shares. This one - a recent install - does not. Thumbnails are generated OK locally, the dconf /org/gnome/nautilus/preferences/show-image-thumbnails is set to always.

Now the most interesting and annoying thing. If I open the folder with gThumb viewer - that generates thumbnails AND the thumbnails can be also seen in nautilus (albeit they are smaller than the standard ones created by nautilus locally.

I tried to execute gdk-pixbuf-thumbnailer in a terminal window that is opened on that share - that works and it can create the output file. Presumably something is wrong with the particular thumbnailer executed by nautilus, but how to find which it is and how it works?

By the way - I installed thunar too - and it does NOT generate thumbnails either locally or on the smb share.

I am having a similar issue. No thumbnails in Nautilus for remote files. It works locally just fine. Gnome 43.2 on with Nautilus 43.1 on Manjaro. If I manually open an image with Gthumb, it generates the thumbnails.