Because there is no official "Windows 10 Lean" ISO from Microsoft today, you have three primary paths: Windows 10 Lean Coming For Low-End Notebooks (Report)
Instead of risking unknown ISOs, create a custom lean image: windows 10 lean iso download 64-bit
Microsoft noticed that budget laptops and tablets with only 16GB of storage could not install standard Windows updates because they lacked the necessary free space. The Solution: Because there is no official "Windows 10 Lean"