I just implemented and released SLIP-0039 password and seed backup. Create M >= N > 1 shares, require any N shares to recover the secret. There's a NuGet library, a CLI and a GUI implementation. See https://www.axantum.com/help#sss, https://github.com/xecrets/xecrets-cli and https://www.nuget.org/packages/Xecrets.Slip39.