The first featured one was Interix, which became SFU and then SUA. Picoprocesses (the base block behind WSL) were introduced in Windows 8.1, where SUA was remov

The first featured one was Interix, which became SFU and then SUA. Picoprocesses (the base block behind WSL) were introduced in Windows 8.1, where SUA was removed (was deprecated in 8.0).