WordPress Playground is made for experiments. However, plugins are not easy to install. If you want to install and use plugins you have to change the URL and add:

&networking=yes.

If you have local storage you will be asked if you want to continue working with the local files. Just answer yes.

https://playground.wordpress.net/?storage=device&networking=yes

Playground is experimental. Some plugins will not run here. So you have to experiment. For example Kadence Blocks work like a charm. Jetpack did not.