@MartynK searching through this forum:
"PIA using pfSense WireGuard Package", post from mid 2024:
https://forum.netgate.com/post/1157847
Or on the Lawrence Systems forum (I think it's about the same but with more posts):
https://forums.lawrencesystems.com/t/pfsense-pia-vpn-wireguard/19376/7
Basically, use PIAs manual-connect repo (or someone's who made one for pfSense specifically) to get a regular Wireguard conf.
https://github.com/pia-foss/manual-connections to