Muun has a different backup method that isnt the typical 12-24 word seed, but uses a sort of serial number like recovery seed. Because of that, people say its custodial, but it isnt. Its open source as well, so if you like it then its a solid wallet. The only reason i dont use muun anymore is because of the fees since it does submarine swaps on chain. You'll find that the fees using a true lightning wallet are astronomically better after the initial channel setup fee.