Posting this in case it helps anyone else. If you’re running BTCPay Server and want to get a permanent LNURL for tipping purposes, follow these steps:

1. Open the Lightning Address plugin on the bottom left of your screen. Create a new address.

2. npm install -g lnurl

3. lnurl encode “https:///.well-known/lnurlp/”

So for bob@example.com, it would be https://example.com/.well-known/lnurlp/bob

4. Copy the output minus the trailing “%”

Idk if theres a simpler way to do this but this is what worked for me