PureBoot + FreeBSD installer

Hello all, I’d like to try running FreeBSD on my Librem 14 (the Atheros AR9462 wireless card is not currently supported in OpenBSD).

However, I’m running into an issue booting to the FreeBSD USB installer from PureBoot. So far, I’ve tried downloading the .img file provided by FreeBSD, confirming the integrity via SHA512, writing it to an empty USB using dd, and then booting to it from the PureBoot menu, and it crashes and boots to the recovery prompt.

In desperation I also tried writing the .iso FreeBSD file to USB, and it still doesn’t work. Both the .img and .iso based drives DO boot in my system76 laptop which does not use coreboot/pureboot.

Has anyone run into this? Is PureBoot unable to boot to some installation media?

I’ll admit my initial post was done with very little knowledge of the boot process and how PureBoot is built. Having done a lot more research, I now understand that I’m asking if Heads (a linux-based coreboot payload) is somehow able to kexec into a BSD kernel, which is obviously non-sensical.

So my follow-up question is this: has anyone tried to build a BSD-based heads, or is tamper-evidence via Heads simply out of the question for someone trying to boot into BSD? My only choice is coreboot+SeaBIOS?