It's been a while, but the most rewarding experience I had in this space was engaging directly with a small local charity. I just pitched them the idea of me getting 10 minutes with every worker that had to use a PC as part of what the charity did. I used the time to interview them, and try to identify something that affected the largest swath of workers.

As it turned out, what I helped them with wasn't code, but a bit of configuration and tuning, but they said it honestly created about a hour of time back per day for most of the workers. There was part of a flow that would often grind a long time and/or error out. Making that fast and reliable was the best low-effort thing I could deliver.