By the looks of it, support for Instant Tethering is in the process of expanding to include devices running on Chrome OS, such as Chromebooks. At the moment, there is no official confirmation on this from Google, however, the feature seems to be live in the Canary channel of Chrome OS. Although, how widely usable it is, is something else entirely. Either way, as the feature is now showing up in an early version of Chrome OS, it does stand to reason that over time it will begin to be expanded out to the more stable versions of Chrome OS, and in turn, most, if not all, Chromebooks.
The current feature was first reported on by Chrome Story and seems to be rather simple in its approach. All the user has to do to get started is be on the Chrome OS Canary channel, enable the 'Instant Tethering' flag, and restart the Chromebook. Following which, Instant Tethering will be listed in the Chromebook's network settings and can be toggled on or off at will.
Instant Tethering is a feature that was launched by Google earlier this year and is designed to allow Google Pixel and Nexus owners to share their mobile internet connection with other devices. Up until now, this has largely been used for sharing a connection between a phone and a tablet. So the expansion of the feature to devices such as Chromebooks will prove invaluable to users when away from a stable and reliable Wi-Fi connection. However, as this is largely a Pixel/Nexus perk at the moment, Chromebooks owners will only be able to make use of the feature, providing they have a Pixel or a Nexus phone. As the initial connection between the phone and Chromebook will need to be activated first. To do so, head into the Pixel/Nexus settings, then to the 'Google' section within settings, followed by clicking on the 'Instant Tethering' tab, and lastly toggling on the feature. Once the initial connection is setup and permission between the two devices has been granted, that will largely be the extent to the phone's inclusion in the process. From then on whenever a connection is needed on the secondary device, providing it is linked to the same Google account as the Pixel/Nexus phone, the user will be able to manually connect through the Chromebook settings.