Lambert, as himself, would definitely have had something to say about Yuya being taught by Strange, but this halved version of Lambert acknowledges it as a practical step to take.

"Sensible of him," he agrees, simply. "The militia can't be everywhere. People have to be able to protect themselves, including being able to get places when they have to. But you'd better make sure to ask him about managing the downsides too." He does flash a quick, wry smile then. "I'm sure Gongezaka wouldn't appreciate you accidentally getting yourself trapped in a mirror."

Being the idealized version of himself doesn't make this Lambert any better at magic, unfortunately, since it's not a skill he would ever particularly claim. He does, however, touch a hand to his chin and take a moment or two to think about Yuya's problem.