I imagine you're not alone in this, and I really hope you find meaningful work that gives you a sense of purpose.
One I can think of that matters to me is not-for-profit education software that is better and cheaper than the for-profit software I was frustrated with as a teacher and which runs on gnu/linux. This is a much larger bag of worms, though, and my reaction to authoritarian school administrators, poor tech support of the software, and an approach to education that felt subpar compared to what I understand from Make it Stick: the science of successful learning (Brown, Roediger and McDanial, 2014), other books, and my own experience in public & private education.
Another important field is early childhood education, though I'm not sure what software is used at that level.
Climate-change modeling, ecosystem modeling as climate changes, anything to help us adapt faster and decrease the amplitude the effects of what we've done to the planet over the past couple centuries?