I prefer ability to force boot a known good FOSS OS from SD card, rather then depending on the SoC vendor or OS vendor to have implemented all the crypto at all

I prefer ability to force boot a known good FOSS OS from SD card, rather then depending on the SoC vendor or OS vendor to have implemented all the crypto at all levels correctly to verify the bootloader, trusted firmware, kernel, kernel modules, userspace programs, and so on. "Known good externally sourced" is better then "maybe verified by in-device mechanisms, but we don't really know", when you have reasons for doubt, about someone potentially modifying the software on your phone. It's not either/or. Making it harder to modify the software via secure boot is good. But having ability to actually run and verify the software from a real point of trust, not just based on some random crappy crypto someone somewhere thrown together for "secure boot", is essential.