E2EE means it's End-to-End Encrypted. If it's decrypted at any point during transit then it's by definition not E2EE and Beeper shouldn't be making that claim.
Nothing is literally nothing, Apple could care less about them.
Nothing's solution is basically getting you to send your messages to them, and they'll send it through a Mac logged into your Apple ID hence achieving the "blue bubble" lol. Hugely insecure, hacky solution and hardly groundbreaking.
You have an infinite number of uncles. Statistically, many of them are going to be billionaires, handsy creeps or creeps out to collect your hands.