The Chrome for Android beta app has been updated today in the Play Store, upping the base code to Chrome 66 for the mobile browser. The new version is build 66.0.3359.30 and represents the first Chrome 66 beta for Android.
Unlike other beta programs in the Play Store, there is no sign up to get the Chrome beta for Android. You can download it here and install it on your compatible devices. Like all beta software however, its not recommended to run it as your daily browser or deploy it into production as there are likely still bugs to be found and there could be performance issues.
Given this is the first Chrome 66 based build for the Chrome for Android beta, there is a lot of bug fixes outlined in the Git for the release. Most of the issues have to do with UI but there are also a fair number of fixes for Virtual Reality (VR) in this update too. It appears that the Chromium team is focusing on improving the overall experience by trying to get rid of some of the oddities that happen when you use Chrome in a VR headset.
The updated app is in the Play Store now if you want to give it a try. Remember, you can use both the Beta app and the Stable version of Chrome on your phone so you can test things out and do a stare-and-compare of features.