What I've tested and works very well so far:
No man Sky: Works perfectly with two open instances of Steam.
The Division 2 opens normally and does not need a Sandboxie, just the virtual machine.
Portal Knights: Another game that normally works with SandBoxie.
Bordelands 2: Two instances open normally, but one of them does not connect to the server, but it is possible to play via Lan.
I installed Warframe, two instances open, but one of them does not connect to the server, I did not find a way to circumvent this.
Share what you have been testing there.
The Division 2 opens normally and does not need a Sandboxie, just the virtual machine.
Portal Knights: Another game that normally works with SandBoxie.
Bordelands 2: Two instances open normally, but one of them does not connect to the server, but it is possible to play via Lan.
I installed Warframe, two instances open, but one of them does not connect to the server, I did not find a way to circumvent this.
Share what you have been testing there.