What do you use as preview environment?

im speaking with a lot of startups while building Autonoma (https://www.getautonoma.com) and im seeing that preview environments are a main issue most of them face, unless they deploy on Vercel/Netlify/Render.

wondering what alternatives have people found to sort this out.

preview envs seem to provide a huge upside for testing and overall engineering workflows but are not easy to configure so we are considering building a standardize way to do this. would love to get people thoughts on the topic