Currently, VyprVPN only support L2TP for Chrome OS. However, Chrome OS Store has several VPN clients, and Chrome OS also allows 'force installing' any program, including a VPN using the admin console. It's what their official page says here: https://support.google.com/chromebook/answer/1282338?hl=en

For those living in China, the Chameleon protocol would be much appreciated as it would enable us to make our chromebooks work better.