Muun is not a lightning wallet.
See title. Muun is an on-chain wallet which uses submarine swaps to interface with lightning. Every transaction with Muun involves an onchain transaction, even if you're 'using' lightning.
Running your own node and managing channels is the cheapest option, but even if you don't want to do that, Acinq's Phoenix Wallet, and Breez Wallet are both non-custodial lightning wallets which require no channel management and do not require you run your own full node (they run a Neutrino lightning node on your phone with channels connected to their nodes). While they are more expensive than running your own node and managing channels, they are faster and cheaper than Muun... Because they are actually Lightning wallets.
Almost every time someone complains about their experience with Lightning to me, it turns out they're using Muun. Stop it.