Hi Ivan,
Though I understand your desire for practice work, but if you are newbie as you say, how much value do you think you can add to a project? Most likely, you'll need extensive help of a senior and/or will make bugs or produce suboptimal code.
Additionally, OutSystems is an expensive product. Charities don't use it, it's used in Enterprise businesses. And they wouldn't want to "hire" a volunteer that's not guaranteed to commit, and has no coding experience.