I have a bluboo mini phone with marshmallow 6.0 installed. It comes with some non-descript launcher called "phenix" installed.
My favorite launcher is line launcher, it doesn't matter what other launcher I install; I can never set it as the default with constantly getting a popup message telling me to chose one, and do I want to use the one I choose, always, or just once? I always choose always, and it never does always.
Going into settings and disabling phenix doesn't do anything either. Neither does removing any and all permissions for phenix.
PS: I also went into the line launcher settings, and set it as the default app there. Still no good. (bluboo mini is a chinese phone).