The best Compatibility Layer alternative to Windows Sandbox is WinBoat, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to Windows Sandbox and three of them are Compatibility Layer Tools so hopefully you can find a suitable replacement. Other interesting Compatibility Layer Tool alternatives to Windows Sandbox are Parallels Desktop and Karton.
Windows Sandbox alternatives are mainly Compatibility Layer Tools, but if you're looking for
Virtualization Tools you can filter on that. Other popular filters include
Windows + Free. These are just examples - use the filter bar below to find more specific alternatives to Windows Sandbox.