Gimp 2.10.x as a snap does generate thumbnails for .xcf files and stores them in ~/snap/gimp/common/.cache/thumbnails/
In most case no need for a specific thumbnailer, anyway gnome-xcf-thumbnailer is no longer available in 20.04 repositories as it’s old piece of software which seems not compatible with latest .xcf format from Gimp 2.10.x. see https://gitlab.gnome.org/GNOME/gimp/-/issues/278 and https://gitlab.gnome.org/Archive/gnome-xcf-thumbnailer/-/merge_requests/1
Nemo, Nautilus and others can display those thumbnails generated by Gimp, only problem here is their location.
If
django@ASGARD:~/.cache$ ls -la
(…)
lrwxrwxrwx 1 django django 47 juin 11 02:47 thumbnails -> /home/django/snap/gimp/common/.cache/thumbnail
then
any app can use those thumbnails for .xcf
hence
1⋅ how tell my session to look for thumbnails not only in ~/.cache/thumbnails/ but also in any thumbnails folder inside ~/snap/ ? Then it would solve the issue for any snap app eventually generating thumbnails.
2⋅ reading again snap doc I wonder if https://snapcraft.io/docs/thumbnailer-service-interface might be the answer. Should I connect that interface to Gimp ? ( after I get back to initial situation regarding thumbnails folders ) Or doesn’t it do what I’m looking for ? if it does then that interface should be connected by default to the snap package. see below
My actual setup is not desirable : all my user’s thumbnails are in a subfolder of Gimp which does not make sense, only for having .xcf thumbnails displayed in any app.
later :
django@ASGARD:~$ sudo snap connect gimp:thumbnailer-service
erreur : snap "gimp" has no plug named "thumbnailer-service"
django@ASGARD:~$
so it answers 2⋅ and lets 1⋅ as the only thing I can think of.