If you want to install Oracle SQL Developer on your Windows computer for free, check if you meet the requirements and then go through the instructions mentioned here.

To install Oracle Database on Windows for free, download Oracle database files, install Oracle, and then set up Oracle using this guide, ...

The Developer Edition of SQL Server is not set up for Remote connections by default so I had to enable TCP/IP in the SQL Configuration Manager for the Database Servers.

You can treat SQL Server on Linux as a new deployment option, not a whole new database. That means you can choose the operating system that best fits your project.