What is the ruling on benefiting from a protected internet network that connected automatically, knowing that its owner is non-Muslim? And is what was published, such as religious lectures, considered ongoing good deeds?

It is not permissible to connect to wireless networks without the permission of their owners, whether they are Muslims or non-belligerent disbelievers. Using these networks to upload lectures and the like does not permit connecting to them without permission. As for the lectures that were published, may Allah reward you for them if you were unaware of the ruling.