How to setup VPN on Raspberry Pi 3 connected to Mesh System

Howdy folks!

I have a raspberry pi model 3 B+. I want to install ProtonVPN on the raspberry pi usinVPN or somthing similar.

Ideally I am hoping to hardwire the raspberry pi to my ISP modem/router then have the Raspberry pi run the VPN software. Then, since the raspberry pi only has 1 physical Ethernet port, use a USB Ethernet adapter and direct the VPN internet out of the USB Ethernet adapter into my TP-Link Deco Mesh System.

Is it possible to have the incoming internet be form say ETH0 (built in Ethernet port) and then send internet into the Mesh through say ETH1 (USB Ethernet adapter)?

This way the entire mesh network can be VPN secured household wide and the raspberry pi can be connected between the ISP modem router & my mesh system?

Thanks in advance! I am really looking forward to some help since I have posted this on Reddit in the Raspberry PI group and never gotten and comments at all 😔!

-M