Calling REST/HTTP API server through VPN from Meteor server deployed on Galaxy/Digital Ocean/Wherever


I need some hints, my Friends. The server part of my Meteor application is heavily calling REST/HTTP services on a customer server that is accessible only via VPN. On my development computer, I simply connect to the server with OpenVPN and I can call directly the REST services. When I deploy my application on a hosting system (Galaxy/Digital Ocean/Zeit/Wherever), can I configure my application to open a VPN to that REST API server?
If yes, can I configure multiple VPN channels/tunnels to multiple REST API servers of multiple customers from the same Meteor server host system? The idea of my Meteor application here would be to provide a service to multiple customers, where the actual data are hosted on the customers REST API behind their VPN.
The deployment workflow would be that, when a new customer wanted to use my service, implemented in Meteor, the customer would give me the details of its VPN and REST server credentials/URL, I’d configure the VPN connection, and then the customer could start using my application service written in Meteor right away.
The other option would be to open a dedicated subscription on Galaxy/Digital Ocean/Zeit/Wherever for each of my customers, deploying my application for them dedicated. If and when the project were successful, I’d automate the process later.
Thank you for your help.