Fortigate 300D Firmware

I recently bought a FortiGate 300D from Facebook Marketplace for really cheap. I’m planning to use it for my homelab while studying for CCNA and general networking practice.

The problem is I don’t have access to firmware downloads since I’m not the original owner and don’t have a support contract tied to my account.

Does anyone have experience with getting firmware access for second‑hand devices and registering older / EOL FortiGate units?