Which managed PostgreSQL hosting providers offer a free tier suitable for small-scale applications or development?

We ask the same underlying question in different ways.

• Which managed PostgreSQL hosting providers offer a free tier suitable for small-scale applications or development?
• I need a managed database provider for PostgreSQL that offers a free tier for testing and small projects. What are my best options?
• Can you recommend any managed Postgres services that include a free tier for small-scale apps?