There is a fairly simple way to get involved in Gutenberg development. One can download a special Gutenberg plugin that includes a Pull Request (PR) of a feature being worked on.
It involves going to Github and clicking the Pull Requests tab https://github.com/WordPress/gutenberg/pulls then looking through the list to find a feature you would like to try out. Click the PR read through what it is about then if you decide you want to test out the feature follow these steps.
Here is an example which I also show in the below video.
1 – I want to test out Shauns new iteration of the user interface for Link design. I new it had the label of “Needs Design Feedback”. I found a PR with the label and clicked it. Clicking the label shows all the “Needs Design Feedback” PRs. There I located Link UI: design Iteration from Shaun Andrews.
2 – Entering the PR. I notice Conversation – Commits – Checks – Files changed tabs.
I clicked the Checks tab. On the left side are various options one can click.
I clicked the Build Gutenberg Plugin Zip.
It enters a Summary page. On the bottom is the option to download the gutenberg-plugin.
I download the plugin and then unzip the zip file. This special zip has another zip inside it. Both are unzipped.
I then need to zip/compress the folder that has become unzipped. This is the plugin I need to upload to a test site and test the feature.
I upload the newly created Gutenberg zip file to a test site. Activate it and go to a page or post and test out the feature.
Here is a video showing the above steps.