ZFS on Linux: Which mountpoint option when mounting manually per script?

I use zfs on luks with portable drive. I have never had problems with the standard mount points. Mounting doesn’t happen until after the pool is imported, and that won’t happen until after the luks volume is unlocked. So I think you may be over thinking this.

Anyway, if you really want to, go with legacy for manual mounting.

I've been using ZFS pools on LUKS encrypted volumes for the better part of a decade. It works fine.

There is no reason to mount the pool manually to attempt to defeat nonexistent timing problems. Just create your pool normally and enjoy.

To avoid any problems in the future, when creating and managing the pool, use the names beginning with luks- in the /dev/mapper directory to refer to the devices. For example, the devices:

lrwxrwxrwx. 1 root root 10 Jul 26 22:22 luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WCC1P1046856 -> ../../dm-5
lrwxrwxrwx. 1 root root 10 Jul 26 22:22 luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WCC1P1145175 -> ../../dm-4
lrwxrwxrwx. 1 root root 10 Jul 26 22:22 luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WCC1P1165144 -> ../../dm-2
lrwxrwxrwx. 1 root root 10 Jul 26 22:22 luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WMC1P0DHH53R -> ../../dm-3

correspond to:

  pool: srv
 state: ONLINE
  scan: scrub repaired 0B in 0h42m with 0 errors on Tue Jul 30 14:42:04 2019
config:

        NAME                                                 STATE     READ WRITE CKSUM
        srv                                                  ONLINE       0     0     0
          mirror-0                                           ONLINE       0     0     0
            luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WCC1P1046856  ONLINE       0     0     0
            luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WCC1P1145175  ONLINE       0     0     0
          mirror-1                                           ONLINE       0     0     0
            luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WCC1P1165144  ONLINE       0     0     0
            luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WMC1P0DHH53R  ONLINE       0     0     0

This pool is created with:

zpool create -o ashift=12 srv \
    mirror \
        luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WCC1P1046856 \
        luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WCC1P1145175 \
    mirror \
        luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WCC1P1165144 \
        luks-ata-WDC_WD2000FYYZ-01UL1B1_WD-WMC1P0DHH53R

You don't need to use none or legacy as mountpoint even if there is some delay with the LUKS drives and if you decrypt these by a script as long as you add zpool import <poolname> after the loading of the drives. Because at the time ZFS wants to import the pools they may be not available which can be seen by a message in syslog