Hello Antonio,
Little late, but may be you can check the below thread.
Here its is explained how system will determined regional setting including decimal notation.
Basically, it is not possible to change the setting globally for all the users in the system and it should be changed by each employee or manually via application and User Management -> Business User for each employee.(If business users are already created via migration or manual creation)
In case business users are not yet created in the system, derivation logic explained in the thread can be helpful.
Hope it helps.
Regards,
Harshal