Hi Simon,
Unfortunately we never solved it, but I’m pretty sure it was impossible with just Hubspot and FB. The only solution would have been to use a 3rd party integration, e.g. Zapier.
I know Hubspot is working on improving this so eventually it will be possible as a direct integration. Though if you look at the LinkedIn CAPI for Hubspot, that is via Zapier, so I’d say Zapier is the safer solution than direct Hubspot integration. Zapier has a long history of successful implementation.
BR, Tertsi