Fees vary depending on the channels used in a payment route, and because payments aren't handled by centralized processors or stored in a blockchain, determining the global average isn't possible.

Some nodes charge 0 sats for routing through them, others charge much more. IME I've never been charged more than 1%.

Although Darth can be a bit aggressive about Muun, he's right. When you make or receive payments with Muun, you're actually swapping on-chain funds to lightning and vice versa.