The technical investigation is impressive.

I'm wondering if the author contacted the JAXA team. Maybe they would share how the data is encoded?

If the information is secret, it's probably encrypted (SpaceX eventually did that once radio amateurs decoded the video stream), but if it's not, maybe JAXA would be happy to help?

As they are, with permission, squatting on HAM frequencies, it should not be encrypted.

Encryption is not allowed on amateur frequencies.

Those regulations don’t apply on the Moon.

Radio waves don't stop when they leave the moon. Those regulations most definitely apply on Earth.