Muun does not support lnurls or lightning addresses. Tldr; Lightning addresses are cool, but they aren't sovereign, so you can't use a sovereign wallet like Muun to integrate with nostr. These are actually not lightning native features, they're like layer 3 tech but it isn't a real layer. They require web servers and if someone else is running that web server, that someone else could rug you -- they can't take the money in your wallet, but they can redirect payments meant for you using the lnurls and lightning addresses away from your wallet and to their own. Muun is a self custody wallet, you own the money in the wallet and invoices that you use to receive payments send money directly to your wallet. They aren't middlemen in the active sense or in any sense where your money could be taken. This is the same with my favourite wallet Phoenix Wallet. Custodial wallets like Wallet of Satoshi, Minibits and others support this, but the only way to retain self sovereignty and use lnurl and lightning addresses is by running your own bitcoin and lightning node and then adding the appropriate software to support it. I, and I'm sure many others, use custodial wallets for zapping and receiving zaps, but only keep small amounts on it while we keep the most of our bitcoin on sovereign wallets like Muun or Phoenix.