I have dedicated one laptop (Macbook2.1 with Libreboot) for photography. I
have Parabola there instead of Trisquel, so this advice might not apply.
Here's what I use:
- for photo tagging, organizing and modifying: darktable
- for touching single images (both RAW and jpg): rawtherapee (darktable is
better)
- for general graphics: GIMP
- for transfering photos to my other devices: syncthing
- for taking backups: duplicity
- for aligning images (e.g. panorama or noise reduction by stacking): hugin
- for calibrating the colors of the screen: displayCal with a colorhug2
colorimeter
Earlier I did try shotwell (I didn't like it), and digiKam (too complicated).
Useful links: https://pixls.us/ for free software tools for photography, and
the blog of one of the founders contains many interesting tricks
https://patdavid.net/archive/
