I use ExpressVPN, and on Android I have an app that will allow me to choose which apps run through the VPN. Everything else uses normal traffic. I can also install ExpressVPN on Ubuntu, but it doesn't have the split tunneling feature.
I set up OpenVPN to use my VPN, but when I turn it on, it routes all my traffic through it. When I check 'Use this connection only for resources on this network', this seems to allow my LAN traffic to stay off the VPN.
However, I only really want one or two applications to use a VPN: Firefox, and maybe a podcatcher. I cannot, for the life of me, get any of the split tunneling tutorials to work for me. I installed Qomui, which won't load my VPN. I followed a tutorial where I create a new user called 'vpn' and run apps as that user, but the script threw an error and the applications wouldn't start.
I run OpenWRT and I'm open to setting up the VPN on the router itself, if this is going to be easier. But I'm going nuts trying to figure this out so if anyone has a good GUI, tutorial, script, or other solution, please let me know.