I have a job offer from a company which provides SaaS based product focused on advertisements and revenue management.

It’s product is used by Entertainment and shopping brands and websites. Now days we know how it is, Entertainment has mixed content and involves things which are forbidden in Islam.

So can I work for this company. I will be working
for the company and not directly for the Entertainment Brands.

Will this be Rightful Sustenance?

If your job has no involvement in haram things, then it is allowed.