When I create a Lighting Network address in BTCPAYSERVER it has a @umbrel.local:3003. How is this accessible to the outside world. Seems like I would need a sort of dynamic dns service for this.
Does BTCPAYSERVER register my username prefix and use that to track destination?
your BTCpay server is “visible” to outisde world ONLY through Tor onion address.
When you generate that LN address you should open BTCpay using the Tor onion address (specific for your BTCpay).
Or look into Guides section of this forum and you will find a nice guide about how to use BTCpay on a clearnet address (IP/domain).
my assumption was I would create a username@mybtcpayserver.com type address and anyone could send lighting payments to it.
my hang up is the @umbrel.local:3003 for that to work it seems like my username must be registered in some lighting address system which would then link to my TOR onion address in order to know where to direct the funds.
Lightning address depends on a service that converts that domain.com into a LN invoice.
It is explained in this guide and how to achieve it
https://darthcoin.substack.com/p/how-to-use-lightning-address