We are ending support to customer screen sharing (or) joining a remote support session from Linux on Jan 31st, 2015.
A couple of factors led us to take this call.
However, you can start a remote support session from Linux and support your customers in Windows or Mac as usual as it's entirely browser based. We may start supporting Linux screen sharing again in future if there is a need.
If you have any doubts or questions, please let us know.