Helios struggles to install on System76 Thelio

I have a System76 Thelio that I'm trying to install Helios on, with the assistance of @jclulow.

After unsuccessfully fighting with the hybrid ISO image for a while (UEFI firmware never recognizes the USB stick w/ the ISO dd'd onto it as a bootable device), jmc gave me an ESP style tarball to extract onto a FAT formatted USB stick (/staff/dock/helios/for_trey/trey.tar.gz). Using the ESP tarball, the Thelio is able to boot from the USB stick into the installer, but we ran into other issues.

Persistent symptoms:

• dladm never shows any links (the thelio has both a wireless nic and an ethernet nic).
• diskinfo never shows the USB stick, just the 2x2Tb NVMe drives
• ls -l /dev/rdsk/*p0 never shows any entries for the USB stick
• dmsg / tail -f /var/adm/messages show the USB stick removal / addition, as well as the kernel indicating the storage is online

What we've tried:

• fmdump -ereports lots of ereport.io.pci.fabric and a handful of ererport.io.pciex.a-nonfatal / ereport.io.pciex.rc.ce-msg entries
• /usr/lib/pci/pcieadm show-devs shows 20 or 30 entries. A fair amount of unknown devices (amdzen_stub{number}, xhci{number}, and pcieb{number}) and no ethernet NIC -- wireless NIC is present though.
• fmadm faulty reports an issue with dev:////pci@0,0 "faulted and taken out of service" as a result of unexpected_telemetry
• fmadm repaired dev:////pci@0,0 returned fmadm: recorded repair to of dev:////pci@0,0 and further runs of fmadm faulty returned nothing... however dladm still has no output and diskinfo / ls -l /dev/rdsk/ doesn't reflect the USB stick at all

jmc suggested I ship the hardware to the emeryville office for further debugging, which I will be doing.

Screenshots from debugging session below.