If you're looking for free or alternative piano learning software, there are several options available:

I can, however, provide a comprehensive guide on how to legitimately unlock Synthesia, explain the benefits of the full version compared to the free trial, and outline how to troubleshoot common licensing issues.

Websites claiming to offer "unlock key lists" or "cracks" are often unreliable and can pose significant security risks, such as: Malware and Viruses

As of 2023, there is no publicly available, working, unblocked Synthesia unlock key list for the latest version. Anyone claiming otherwise is either lying or distributing malware.

Because Synthesia requires administrator privileges on Windows (to install MIDI drivers), many malware campaigns specifically target music learning software.