You don’t necessarily need to know anything about Agile to be a project manager, since only some companies use project managers at all. (There’s a big difference between a product owner and a project manager, and they sometimes coexist.)

The idea that nothing has changed and that you don’t need to learn anything new is so offensive I don’t even know where to begin. (My anger is directed at the recruiter here, not you!)

The best course I’ve seen is Coursera’s Agile Specialization, which packages together several short courses for complete end-to-end product development. It combines Design Thinking, Scrum, Kanban and XP and is very practical and user-centric.

I combined that one with Udemy’s Product Management course and a short Scrum Master prep course for a well-rounded intro to the concepts — in all, that’s about eight months’ worth of course, but I was very keen and did it in three rather intensive months. That seems like a lot, but interview panels were very impressed with my knowledge at the end of it.

Good luck with it all — and remember, Agile is not something you do, it’s something you are.