@Danp Good catch, can't believe I missed that.
Unfortunately, that produced a new error;
Error code: SR_BACKEND_FAILURE_77
Error parameters: , Logical Volume group creation failed,
From some googling around it appears the issue is that the disks still have a zfs_member tag on them. lsblk -f produces this:
NAME FSTYPE LABEL UUID MOUNTPOINT
sdd zfs_memb
ββsdd2 zfs_memb data 305869021769108511
ββsdd1 zfs_memb
sdb linux_ra localhost:127
1d7d1927-dfdb-c8a8-4af1-b25c2b355a7a
ββmd127 zfs_memb boot-pool 17799519329276801846
ββmd127p5 ext3 logs-efkbam 0deeb614-6788-45f9-92b7-0f6acc05da6d /var/log
ββmd127p3 zfs_memb boot-pool 17799519329276801846
ββmd127p1 ext3 root-efkbam 62e0f462-29f8-4c2a-8df7-bed45c144a4a /
ββmd127p6 swap swap-efkbam 26a6ce99-d4fd-43d1-8a27-79bddafb8707 [SWAP]
ββmd127p4 vfat BOOT-EFKBAM 0B9B-C4C7 /boot/efi
ββmd127p2
sde zfs_memb
ββsde2 zfs_memb data 305869021769108511
ββsde1 zfs_memb
sdc linux_ra localhost:127
1d7d1927-dfdb-c8a8-4af1-b25c2b355a7a
ββmd127 zfs_memb boot-pool 17799519329276801846
ββmd127p5 ext3 logs-efkbam 0deeb614-6788-45f9-92b7-0f6acc05da6d /var/log
ββmd127p3 zfs_memb boot-pool 17799519329276801846
ββmd127p1 ext3 root-efkbam 62e0f462-29f8-4c2a-8df7-bed45c144a4a /
ββmd127p6 swap swap-efkbam 26a6ce99-d4fd-43d1-8a27-79bddafb8707 [SWAP]
ββmd127p4 vfat BOOT-EFKBAM 0B9B-C4C7 /boot/efi
ββmd127p2
sda
ββsda1
So it appears my next step is sorting that out. Unfortunately the only way of clearing these tags that I've found so far seems to be wiping the drives completely and starting over? If so that's going to suck as I don't have physical access to the machine right now.
If anyone has any suggestions for removing errant zfs_member tags (this machine previously hosted a TrueNAS install) without wiping the whole damn machine, I'd be eager to hear them. If not it'll have to wait until I'm back in the office I guess.
Thank you again @Danp for your help.