Desiring LUKS basically rules out image-based distribution, so to find a compatible installer this [0] page was useful. I opted for straight Debian (bullseye). This amounts to a script wrapping debootstrap that adds in the local firmware and kernel patches. I was required to use a sufficiently fast and large microSD card (16 GB+). As reported on [1] and in the dedicated thread [2] there are a few small issues:
* firefox does indeed crash in the way described, though I expect this will resolve itself after an upstream update
* The brightness up/down keys do not work, though they do in the base image
* I've encountered issues with the wifi getting wedged after resuming from sleep.
Still, on the whole it seems snappier than the base image, and the track pad latencies issues I noticed there don't seem to manifest here.
[0]: https://wiki.pine64.org/index.php/Pinebook_Pro_Software_Rele... [1]: https://wiki.pine64.org/index.php/Pinebook_Pro_Debian_Instal... [2]: https://forum.pine64.org/showthread.php?tid=8487
edit: formatting.