(Replace D: with your Windows USB drive letter).
"Why does a modern, fast-paced MOBA game need a software framework from 2007?" net framework 3.5 league of legends
Windows Feature window opens, attempts to download .NET 3.5, and fails with error code 0x800F0906 or 0x800F081F . (Replace D: with your Windows USB drive letter)
After that, reinstall League of Legends (the repair tool will work properly with a healthy .NET 3.5). attempts to download .NET 3.5