Properly secure symmetric encryption needs a key with at least 128 bits of entropy. In the "device lost/stolen" scenario, that key must not be on the device. Key inside a TPM on the device itself is DRM, nothing more. There's better and worse DRM, I think the iPhone bootloader one is one of the better ones, but it's still just DRM.

You either need to enter a 128-bit entropy password on every boot (good luck with that) or you need to hold it on some external device, with some variant of USB / smartcard / NFC / Bluetooth to transmit it. NB. this is one of the cases where the usual "key for signing only, never leaves device, ephemeral DH and ZK protocols" like for SSH will not work on its own; you need the high-entropy key physically separate from the device.

The NSA realised this a while ago: https://en.wikipedia.org/wiki/KSD-64

Linux/LUKS etc. doesn't change any of this, by the way.

P.S. If Eclipse really has beef with Microsoft, he could always make an exploit that lets you set up a PC without making a Microsoft account.