Ask HN: How to volunteer for social causes as a software engineer?

Hi Everyone - I'm interested in spending some time (~20h a month) volunteering to help social causes. However, my latest attempts were pretty disheartening. One charity had me answering phones, another doing basic IT work. I didn't feel remotely utilized, and felt I would have a much larger impact donating a few hours salary than a few hours of my time.

Other professions (lawyers, doctors) seem to have great frameworks for pro-bono work utilizing their skills to make a significant impact. Does anything like this exist for tech? What's step 1 of getting involved, but in a way that utilizes my skills? I'm interested in both tech-focused organizations/charities, and general approaches for working with existing non-tech charities.

Note: I try to support open source on the side as well, but that's not what I'm looking for here.

Thanks in advance.