I am running systemd, and this page said to pass the kernel parameter fsck.repair=yes to have all filesystems checked.
Trying this, my ESP partition (FAT32) was dutifully checked, but there are no journal lines matching the strings fsck, btrfs, check or the device name which indicate that anything happened on / itself.
I believe that btrfs-check is not being run.
How can I find the last btrfs check date/timestamp of a filesystem?