How to route traffic through an external VPN device that is connected to my router?

My father is coming to visit me in Europe and will need to work remotely while he is here. Unfortunately, he can’t install any other software onto his device. We will try to use a phone connected to a VPN that is connected to the WiFi router but I am worried that the connection might be to slow. Is there any such device that can route his computer to a VPN and then to my home WiFi?

It sounds to me like you want a VPN server at Dad’s house, so that he appears on his home network when he is away from home.

I’m a fan of piVPN. You can read more about it here: https://www.pivpn.io

Edit
This solution would require installation if client software on Dads PC. It seems Dad needs a VPN travel router to talk to the home server. Something like this : GL.iNet GL-SFT1200 (Opal) Secure Travel WiFi Router – AC1200 Dual Band Gigabit Ethernet Wireless Internet | IPv6 USB 2.0 MU-MIMO DDR3 |128MB Ram Repeater Bridge Access Point Mode

Another user will chime in with good suggestions, too, I’m sure.

gl.inet has turnkey openwrt devices. That should fit the bill.