Muun won’t work for that because it doesn’t support the Lightning address LNURL format.

The best options are currently:

Wallet of Satoshi

https://walletofsatoshi.com

Alby

https://getalby.com

LightningTipBot

https://ln.tips/

Both Alby and LightningTipBot can be configured with Zeus to give you an instant mobile wallet.

https://zeusln.app

You can also get an address from other places like Strike, Zebedee, Fountain.fm and Stacker.news.