Thanks Jay, I think I’ve found the issue.
My VPS provider, webdock.io (who are great by the way) don’t support zfs because they use it at the host level; I’m advised nested zfs is a no go. They also didn’t recommend overlay2 for my install and suggested I edit launcher to include the vfs storage driver, which isn’t there by default.
171 Storage Driver: (vfs|aufs|zfs|overlay2)
⬆️
I suspect sudo git pull overwrote this, and then I tried to rebuild with the wrong storage driver?
I’ve just rolled everything back and then re-edited launcher before running rebuild app and everything is working again.
cd /var/discourse
sudo git stash
sudo git pull
sudo nano launcher
then edit line 171 to include vfs
sudo ./launcher rebuild app