Since 2.4.0, BTCPay Server doesn't support LNDHub natively, if you rely on it, please use this plugin to keep support. This plugin adds support for connecting an LNDHub backend to your BTCPay Server.
You can then add the following lightning connection string to your BTCPay Server:
lndhub://login:password@https://lndhub.io
type=lndhub;server=https://login:password@lndhub.io