I doubt many of these exist. And if they do, they're probably small. I tried to go "API-only" for my SaaS. But I was met with abysmal onboarding conversion rate

I doubt many of these exist. And if they do, they're probably small. I tried to go "API-only" for my SaaS. But I was met with abysmal onboarding conversion rates. And I tried to stick it out, too, improving documentation and DX where needed. Ultimately, I didn't get my first paying customer until I built a basic admin UI for the API. Even though a large percentage of my customers don't actually use the UI in their integrations or day-to-day, that initial friction of no UI when learning the ropes was killer.