idk if this is a hot take but I don't think Armin is friendly. I think people find him generally off-putting. Like, people think he looks sweet, but also find him strange; for the topics that interest him, the way he didn't stray far from Eren (& Mikasa) socially, and his general demeanor.

I think that as Armin established himself more as he grew up, he developed better interpersonal skills that compliment his rhetorical prowess. I think he's the type of person who sees value in life and in minimizing harm. He offers kindness to his friends and understanding to all. But I don't see him as particularly "friendly"