If you're referring to Sign My Rocket, it's legit. I've been in the guy's Telegram channel, Combat Footage; the pinned messages have more information, including when the actual website was launched (iirc, it all used to be done via Telegram messages). I believe the older pins explain how he's working with a charity helping the army in Cherkasy. A friend of mine recently bought a signed shell as a birthday gift to himself. Most people will go for the shells since they're smaller and cheaper.

Obvious content warning for the channel itself - as the name says, there's tons of footage from the battlefield that is posted.

Heartwarming: the worst people you know are all fighting!

I hope they shred each other.