What is the ruling on working in the IT department of a global company specialized in online advertising, knowing that the company does not prevent advertisements that violate Islamic law, such as ads for alcoholic beverages and interest-based loans? Is it permissible to work for it?

As long as your work in the company is limited to preparing the advertising platform and programming, and you have no connection to displaying the advertisements themselves, then there is no harm in this work for you. The fact that some advertisements are forbidden does not affect this, for the platform is a means for displaying both permissible and other advertisements, and it is not exclusively dedicated to the forbidden.