Hello. I tried installing Ubuntu Touch with MultiROM and TWRP recovery without kexec-hardboot support enable, with the no kexec-workaround enable in the Recovery options, which resulted in a hard brick. I just want to warm people not to do this. CM12.1, CM13.1 and CM14 do not have the corresponding adapted kernel with kexec support, so don't use them as main ROM if you plan to install Ubuntu Touch, because the workaround available in the recovery will just cause a hard brick.
Beside that, following the steps in this video with the exact same version of software should get Ubuntu installed with MultiROM without any headache