Quotas are supported in specific storage drivers only.
According to the table in the section Storage Backends and supported functions / Feature comparison
at https://lxd.readthedocs.io/en/latest/storage/
the Directory storage driver does not support quotas. ZFS and btrfs do, however.
Well, I realized it that I created zfspool1 in old initiations. I think it remained former config and config looking for it.
root@lxd:/var/lib/lxd# lxc config set storage.zfs_pool_name lxd
error: Error checking if a pool is already in use: Failed to list ZFS filesystems: cannot open ‘zfspool1’: dataset does not exist
root@lxd:/var/lib/lxd# zpool list
NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
lxd 2.98G 274K 2.98G - 0% 0% 1.00x ONLINE -
How can I set the name or recreate it to use ZFS not dir?