I wonder how this is done?
Magic!
And which CLI commands make relation between Qm_HASH_ and subdomainHASH ?
The Qm hash is a CidV0 Content Identifier (CID) which uses base58 encoding.
The subdomain hash is a CidV1 content identifier which uses base32 encoding. It is the same underlying hash, just represented differently.
You can covert between hashes using ipfs cid commands. ipfs cid base32 <QmHash> for example.