Yes, the first page (the 'confirmation of participation' part) of the Youthpass certificates for the 2021-2027 Erasmus+ Youth and European Solidarity Corps can be signed digitally. The digital signature used in Youthpass is a text-based signature confirmation, a so-called simple electronic signature (SES).
While generating the certificates at the 'Generate' step, you are given the possibility to 'Mark certificates as signed electronically':
If you check this checkbox and generate the certificate, the first page of the certificate will include the notice 'Electronically signed on /date/ /time/ by /username/ under the signature field:
Note: The /username/ in the electronic signature text is the 'First name' and 'Surname' as entered in the user account generating the certificate. If needed, you can be change these from the 'Edit your personal details' link on your account:
Unfortunately, the certificates for the older programmes cannot be signed electronically and will need to be printed and signed by hand, if needed.