You want to update the BIOS of a PCEngines APU2 box from Pfsense? It is rather easy.
PC Engines maintains up to date BIOS of these machines at disposal here : https://pcengines.github.io
Here is for my part a very basic script that updates the apu2_v4.10.0.0.rom of the BIOS. You can easily adapt it to your needs:
#!/bin/sh
# Update APU2 Bios
# by Gonzague Dambricourt
# Simple script without any checks, use at your own risk
echo "Flash time for APU"
pkg install -y flashrom
rm apu2*
fetch https://3mdeb.com/open-source-firmware/pcengines/apu2/apu2_v4.10.0.0.rom
flashrom -w apu2_v4.10.0.0.rom -p internal:boardmismatch=force
echo "Finished"
exitA better version can be found here: https://github.com/bouchecousue/PCEngines-APU2-Update-BIOS-from-PfSense
This post is also available in fr_FR.