Render.com currently has free tier that allows users to create a Postgresql database. I created one but had a hard time connecting it to my asp.net core 5 application. After trial and error here are the connection strings that worked:
LocalPostgreSQL: "Server = 127.0.0.1; Port = 5432; Database = postgres; User Id = postgres; Password = <password>"
RenderPostgreSQL: "Host = <location>-postgres.render.com; Database = <database>; Username = <username>; Password = <password>; SSL Mode = Require;"