Some small update
The MPTCP LEDE project previously supported only the stable 17.01 LEDE branch and the latest stable MPTCP kernel branch. Not much after new MPTCP version released or at least started the development of that. So we have the in development branch of MPTCP kernel version 0.93 which is based on the 4.9 vanilla kernel version. Because long term supported kernels also supported by LEDE (4.4 and 4.9 currently) I updated my fork.
What we have now
Master branch with unstable MPTCP supported 4.9 kernel
Lede-mptcp-17.01 branch with stable MPTCP supported 4.4 kernel
Just as before, before the start of building LEDE, its required to run
make kernel_menuconfig then enable MPTCP support in
Networking support -> Networking options section of kernel menuconfig. In the submenus You can select path-manager and scheduler modules to compile.