Forgot to mention my BTCPay instance is hosted. Obviously there is some moderate cost involved. It might be possible to make this work on your home node but in order for LNURL to work you need to set up DNS pointing to your server. In my case I didn't want to expose my home network to the world. There are a couple of one-click installers, see https://docs.btcpayserver.org/Deployment/webdeployment/