BTCPay Server is an Open Source payment processor conforms to the invoice API of Bitpay. This allows easy migration of your code base to your own, self-hosted payment processor.
This solution is for you if:
You currently use Bitpay as a payment processor but are worry about their commitment to Bitcoin in the future You want to be in control of your own funds Bitpay compliance team decided to reject your application You want lower fee (we support Segwit) You want to become a payment processor yourself and offer BTCPay hosted solution to merchants You want to a way support other currency than those offered by Bitpay
Deployment is very well described and proposes multiple ways from manual, containers to hosting. BTCPay Server seems to have a clear future.