I used to work on software for non-profits. I found it fulfilling but it was hard to do the work since I found fullstack technically uninteresting (this is my own shortcoming).

Finding a balance in that is difficult. I have seen that it might be easier to find a societally good job the less technically deep the job gets. Networking research seems to be both technically interesting and connected to societal impact (eg. because of the ties to censorship, security, net neutrality etc)

It seems hard to continue doing this sort of research after your PhD though, as in both your school name matters immensely (i.e. you're screwed if you didn't go to Berkeley, CMU, Stanford, or MIT) and so does your publishing success to land a research job, which seems like an enormous task.