Muun isn't technically a self custody Lightning wallet. Can you do Lightning? Yes, but fees can be as high as on-chain fees sometimes.
Discussion
Muun is self custody. It is not real lightning though.
That being said, it’s my preferred onboarding wallet because receive fees are zero despite not being proper Lightning, and they do get to self custody. I tell them that they will need to understand the base blockchain layer and the true Lightning layer if they really want to learn more, but this is just a starting point. I haven’t found any other balance I’ve been comfortable with for onboarding.