Astronomía Sur Tutorials - Preprocesessing tutorial, batch processing and other functions. Spanish.
Trapped Photons- Tutorials specifically aimed at image processing with PixInsight by David Ault.
PixInsight Basic Processing - PixInsight interface and a basic LRGB processing by Andrea Lucchetti. Italian.
Astrophotography by Herbert Walter - A series of short videos and explanations of everyday or less well-known work steps with PixInsight. In german language.