This is probably going to be unpopular, but whichever stack helps you ship fastest. If you're deploying microservices as a brand-new startup, you're absolutely doing it wrong.

Like others have mentioned, React+TS on the frontend is a great start. On the backend it depends on how technical your team is but Laravel/PHP or Node+TS is easy.

The best stack is the one you can actually ship fast. If your v1 isn't a messy disaster, then you're moving way too slowly.