"Proof of Attendance" has long been worked on in the crypto space, basically giving digital badges to people based on verifiable attendance.

The problem in that space and in supply chains is at the end of the day you still have to eventually trust some thing as the source of truth to verify against. I've done supply chain verification in as simple of a way of comparing the downstream ERP to the upstream (e.g. Brand or Wholesaler) data, but it relies on access to the upstream data and trust that the upstream data is correct. You can reverse the problem by thinking about who has the incentive to try to game the state of the data in the system and what are the most common paths they are going to choose to do so.