How do you evaluate smaller fashion brands from a sustainability perspective?

I’ve been trying to move away from fast fashion and think more intentionally about where I’m buying my clothes from. One thing I struggle with is evaluating smaller fashion brands that aren’t very mainstream. Sometimes they look more thoughtful in terms of design and materials but it’s hard to know what actually qualifies as sustainable versus just good marketing. Recently I came across a brand called Arotagas while browsing dresses, and it made me think more broadly about how people here assess brands like that. When you discover a lesser known label, what do you usually look for first? Fabric sourcing? Production transparency? Longevity of the garment? I’d love to understand how others approach this before making a purchase.