Let's say TPB accept Silent payments. Someone sends them a donation, which confirms on-chain. Nobody else can know TPB is the receiver, because they can't know which on-chain address belongs to their Silent payment.
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You are right, I misunderstood what silent payment is, I thought the transaction will not be available on blockchain, but not like that, it will be available on the blockchain.
I don't think this helps: when opening a LN channel, there's no need to publish your address publicly.
So far the transaction is available on blockchain and transparent to the public but in a way the recipient can not be known (or link to the identity of the recipient), then this (layer 2) is not needed.