Both PostmarketOS (if you use the phosh env) and Mobian use phosh, proc, chatty, libhandy, squeekboard, and a number of Purism packages. Mobian would take a lot more work (and likely would not exist) if they did not take advantage of Purism's work.
Feel free to go through https://puri.sm/posts/ to see their documentation of what they contribute, but here is one post I choose arbitrarily:
Other than PureOS what other "pinephone distros" are using Purism Software? On top of that, how much of "Purism Software" is upstream linux?