Users can enable ZFS features (like zstd) on a root pool even if the installed legacy bootloader (gptzfsboot) is outdated and lacks support for them. This can create a failure: the system runs fine until the next reboot, at which point the bootloader fails to read the pool, making the system unbootable.
This is a proof-of-concept program that checks for the feature@zstd_compress ZFS feature only. Other features that affect bootability will be added.