Ask HN: In hindsight, what would you do differently for a startup tech stack?

I'm mostly curious about the context of a startup (because I'm doing that now). And I'm wondering what kind of things people wish they did in hindsight given their situation.

I for e.g. already wish I had spent a "bit" less time on ideating and a bit more time on getting in to flutter (as now I've gone in to an iOS mode and I know that's not scalable at the start since we won't have man power to maintain an android and ios codebase)