Assistance Requested for Claiming Multiple Particle Boards

I hope this is the right place for this.

As the title suggests, I need help claiming multiple Particle boards that were gifted to me by my grandfather. Unfortunately, these boards have been claimed by his account, which I do not have access to due to his current health situation, and will unlikely be able to access it in the future.

Chris at Particle directed me here for Colleen to assist.

Which devices? Wi-Fi (Argon, Photon) or cellular? The process is different for cellular devices.

Thanks for the reply, and sorry, I should have been more specific! The boards are Photon and Argon.

For the Argon and Photon you can try the technique here: