'Pseudonym' in the signature field in the digital rental contract means that the signer has chosen for their name not to be displayed on certificates when signing with NemID.
The signature is fully valid, even though 'pseudonym' appears instead of the tenant's name. The tenants real name in the rental contract itself is the only place where the tenant's actual name will appear.
Note that NemID was discontinued on October 31 2023, and replaced by MitID. At the same time, the use of 'pseudonym' was changed so that MitID signers with a secret address/name will have a blank field instead of their name.