I encourage you to read what a TPM is. A TPM isn't an "encryption" software/hardware. It's completely orthogonal to "successful open source encryption software".
"successful open source encryption software" don't solve the main usability problem with encryption: "Where do I store my super secure 4096-bit private key so it's both secure and convenient to use"
"successful open source encryption software" don't solve the main usability problem with encryption: "Where do I store my super secure 4096-bit private key so it's both secure and convenient to use"