One can use the instant messaging client Pidgin and Skype. Skype for Business was previously called Lync.
pacman -S pidgin
and install the SIP/Simple protocol for Skype for Business/Office 365/Lync
pacman -S pidgin-sipe
Setting up the account: Use your company mail-address. Protocol is: Office communicator.
In Set up Pidgin messenger and Office 365 Lync one finds the crucial hint that one has to use a special user-agent information string
User Agent : UCCAPI/15.0.4420.1017 OC/15.0.4420.1017
In Pidgin configuration this looks like this:
The post from Gary Woodfine from above states that you also have to specify server, port, and authentification scheme. But you don’t have to. You can simply leave these entries empty, or having their default values.