I just transferred 5 sats from my BlueWallet to my newly created Muun wallet. Cost was 1 sat, instantenous.

BlueWallet I think understand. It is custodial. But Muun wallet.... I thought it was non-custodial? Meaning I need to open a channel, i.e. do a on-chain transaction, before receiving fund via lightning?

This makes me confused. How is this possible in a non-custodial muun wallet?

I feel apprehensive about using Muun wallet. No clear distinction between Lightning balance and on chain balance. A bit too user friendly. For a non-material bearer asset like BTC (first time in human history), a bit more DIY is needed IMO.

Now, BlueWallet is also very user friendly. But they are upfront about being custodial, and also very clear distinction between lightning and onchain.