Miguel Almeida Hello Miguel,
Your need can be met through sync: Windows for one domain and LDAP for the other.
Follow the settings below as an example:

To ensure authentication in all domains (including non-standard ones), you need to configure the login attribute in the additional domains with the specific value: userPrincipalName.
Example:

Additional domain authentication requires the use of the full username, including the domain.

Difference between the two options:
sAMAccountName:
- Validates only the domainless username.
- Use only in the default domain.
main userName:
- Validates the username with the domain (like an email).
- Use in additional domains.
Example:
sAMAccountName: asilva
main userName: asilva@bbsupporte.local