Can you play with two clients up?
Do you have two computers? I know that family members can play simultaneously from the same house, we have a family of four in our guild that can all be on at once. But they are obviously each on their own machine.
Try using Sandboxie
For sure you could set up two separate Windows VMs and run both of them at the same time. You do all of the non-windows stuff for free by installing Linux and VirtualBox.
You can use two windows accounts, using the switch user option in the log off menu to go back and forth. It’s probably the simplest way. You’ll want to disable password logins to speed it up.