Porting PureBoot to the Librem 5 is still on our TODO list but admittedly it is a lower priority than some of our other tasks. I would really love to see it on there though.
A related feature that we did get working is using the OpenPGP smart card reader (or optionally a Librem Key plugged in with an adapter) to unlock disk encryption at boot. Another member in the forum adapted my PureOS script I wrote for the laptops to their phone, and I further adapted their work with a project fork that also works with the embedded OpenPGP smart card reader (and I use this on my own Librem 5). But we have not yet made it a formal project. What I really want to do is combine it any the laptop-focused script into a single all-encompassing one, but again, we haven’t had an opportunity to do that yet.