How do you test demand without spending money on a custom site?

Spent a few weeks building a basic prototype and now facing the usual dilemma do I set up clean domain infrastructure and company emails first, or just share a raw link on socials to see if anyone cares?

It’s way too easy to spend 3 days picking colors and tweaking landing pages instead of getting real feedback.

For those who launch frequently: what is the bare minimum setup you launch with on Day 1?