Is knowing if someone blocked you on instagram still possible?

One more sign that's harder to explain away: a block removes the follow in both directions. So if you followed each other and they've disappeared from your following list without you touching anything, that points to a block rather than a deactivation.

There's no notification either way, so you're reading tea leaves. The usual tell is their profile still loading for you but showing no posts, or search stopping finding them entirely while a different account sees them fine - log out in a browser and compare, that's the cleanest test. Old DMs stay in your inbox but nothing new will send. The catch is that a deactivated account looks identical from your side, so you can never be certain it's a block rather than them taking a break.