I have an oddly-specific networking question that I'm hoping to get solved (and would like to have Lemmy be the home of the solution, in case I stumble upon this myself.)

I have a device that needs to "phone home" on a weekly basis. This device needs to have a static IP in order to be "valid". On windows, I usually can get it to work by starting openvpn, plugging in the external device in question and "routing that" through Openvpn. You do this by simply connecting the external nic and then right click on the nic in the control panel and set the "Allow other network users to connect through this computer's internet connection" along with assigning the external device to the OpenVPN connection. This routes all internet packets from X device to the internet via the OpenVPN connection without a major problem. I should note that it's extremely fickle, and it hurts my ability to remote in the machine on occasion, so I'm looking to change it.

What I'd like on my linux system is to simulate the same setup, but with 1) a permanent "connection" to the openvpn end point that is always available but not used by most networking tasks on the computer (for example, browser will use standard ethernet connection) and 2) The external nic will automatically route itself through the OpenVPN server, acting as a "router" for a (singular) external device that needs to access the internet.

Is this possible? Are there any guides for setting up this kind of complex network setup? Is it possible to do without going crazy and making my computer a full-blown router (like, doing DHCP work and the like)?