Azure App Service now has a free Linux tier and supports Python and Java@20aman Jun 30, 2019
Azure App Service has expanded its capabilities to include Linux as it's hosting Operating System. With the goodness of Linux also comes the support for Python and Java natively.
Now when you will create a new App Service in Microsoft Azure, you can view different Python versions that are currently supported.
You can also view various supported Java versions.
Under the Operating System settings you can see the Linux as an option. Note that based on the Runtime stack selected, this option maybe pre-selected for you and you won't be able to change this setting. If you will select a Runtime Stack that is supported on both OS then you will have the option to switch between the two platforms. E.g. for .Net core you can select any one of the two platforms.