I've met lots of Egyptians in my life, but I've never met anyone from any countries that might claim to use classical Arabic. So if this is for non-Arab world Learners, I imagine that learning the dialect most likely to be encountered is fine.
You may hear the claim that Egyptian Arabic is understood by everyone in the Arab world and that's true. But reminder that Egyptians understand most other dialects. You can imagine a person speaking Qatari with an Egyptian, it's possible that each uses their dialect and understand each other. But that wouldn't be the case for someone that only knows Egyptian.