Can't find /boot/zfsloader

[Mjölnir]

I just checked and all 12.x installs seem to have vfs.zfs.min_auto_ashift=12 already preset (by the installer?) in /etc/sysctl.conf [...]
The sysctl.conf (5)hasn't been touched on any of those systems, so those are the defaults set by the installer. I suspect the ashift is also set by the installer because on the 12.1-RELEASE host the various security knobs are listed before the ashift.

I didn't look into the installer for quite a while (building from source instead & make install{world,kernel} with DESTDIR etc. set), but IIRC the partitioning module of the installer asks if it should align partitions on sector borders? This applies to gpart(8)'s -a alignment parameter, so strictly speaking it's OT and doesn't affect ZFS's newly created vdes. I guess performance suffers on modern large drives with a blocksize <> 512 when this ZFS tunable isn't set. vfs.zfs.min_auto_ashift=12 is the failsafe value for modern large drives with a blocksize of 4 kiB, and on other's it doesn't hurt as long you don't create 1000's of vdevs. BTW you can file in a bug report: this should be renamed to vfs.zfs.vdev.min_auto_ashift