I volunteer as a tutor for an organization that provides academic help to students experiencing homelessness. It's not restricted to people working in tech but

I volunteer as a tutor for an organization that provides academic help to students experiencing homelessness. It's not restricted to people working in tech but my anecdotal impression is that there are relatively few tutors who have strong technical backgrounds and a genuine love for math/science-type subjects If you have such a background and enjoy working with kids you can be quite helpful by (1.) helping students keep from falling so far behind in school that they're unable to pass their classes (2.) providing an example of what it looks like for an adult to be passionate about math and science topics (I think many of these students don't have many such examples). I'm not sure it's the highest-impact thing I could be doing (i.e. maybe I could have a greater positive impact by donating the hourly value of my time to some charity) but if you're interested in boots-on-the-ground volunteer work that involves in-person work I'd highly recommend it.