NEW - summer course at Ferskvandscentret in Silkeborg, Denmark. Course is held in Danish: Find the course here
The two courses below I made some years ago but they are still running successfully on skillshare. For me they are quite funny to watch and a bit naïve on my behalf but I guess they do what they should namely teach animation in a great but totally free software OpenToonz.
Skillshare Course: Easy 2D Animation in the Advanced Open Source Software OpenToonz: Find the course here
Skillshare Course: Importing backgrounds and image sequences into OpenToonz 2D animation software: Find the course here