When I hear full disk encryption, I think of what I'm using: Using the encryption feature of the disk with a password / keyphrase prompt built into the system firmware (UEFI). It is 100% transparent to any software.
The only major downside is that you need to trust the hardware manufacturer (and their FIPS certification), which is fine for my purposes, but might not be fine for state secrets or extremely valuable trade secrets.
I don't know if FIPS standards have improved, but combining my priors about products boasting FIPS and manufacturer code quality in general, I would actively not trust it with any data, full expecting it either leaks them, corrupts them, or somehow both.