I use DNS66 to as a VPN ad blocker. You can lock the app so that clearing running apps won't shut it down, should work for this app too. Just long press on the

I use DNS66 to as a VPN ad blocker. You can lock the app so that clearing running apps won't shut it down, should work for this app too. Just long press on the running window and a lock option should show up. It works for me and I only ever need to manually start it after rebooting my phone.