Avoid. Only 2 GB of RAM and this is no longer receiving OS updates.
As stated above, device is no longer getting updates: https://support.google.com/chrome/a/answer/6220366?hl=en
I just did a (radio) show with a school superintendent. It appears that, until something better/cheaper comes along, Chromebooks are pretty much “standard issue” for students. So expect used school cast-offs (“refurbs”) to be in the bargainsphere for quite sometime. Kinda like AlphaSmarts.
Can you manually install updates?
You can’t force official ChromeOS updates once Google has stopped supporting a device (even though we should merely be talking about browser and Linux OS-level software support that shouldn’t be device-specific and thus should still be available for relevant devices, but that’s a whole other topic and I digress!)
You can still continue to use an unsupported device; I have one of these C720s that I specifically lug around as a “just-in-case,” throwaway device. It works, but may be insecure as it doesn’t have the latest security updates.
That being said, you can still try to install another OS on Chromebooks; I haven’t had to do this myself, but I know that Neverware Cloudready (the open-source alternative to ChromeOS based on the underlying Chromium OS) is an option and is the closest thing to stock ChromeOS. You’d have to enable Dev mode which turns off OS verification and gives you more control over the device.
I’ve loaded linux on one before; it runs off the USB3 pen drive.
It’s not as snappy as a native install but it does work to bring life back to a device that’s been abandoned by the manufacturer. The screen size/resolution is a real killer.