We are running skype for business 2015 hybrid connected to o365. With CU 8 you can move an user from S4B onprem directly to MS Teams. Since I only do the CU updates every so often I forget the process so I’m gathering the links I use her so they are all together and easy next time I need to install a CU.
https://support.microsoft.com/en-us/help/3061064/updates-for-skype-for-business-server-2015
