I have, but only superficially.  Is there an LNURL-pay solution already out there that delivers on the above?

* Untrusted staff member types in the amount on their own device (using only a browser)
* Customer scans & sends (no need for them to type the amount)

EDIT:  this article explained it well:  https://thebitcoinmanual.com/articles/what-is-ln-url-and-how-does-it-work/

I don't think OpenNode have LNURL-pay (I could be mistaken).  is there an easy-to-sign-up LNURL-pay service that also provides auto-fiat conversions?