If SELinux Mode Changer doesn't work, and you are properly rooted, then your kernel likely isn't compiled with permissive mode and was compiled with the flag
EXTRA_CFLAGS += -DCONFIG_ALWAYS_ENFORCE=true which doesn't allow permissive mode to be set in anyway.
You will need to get the kernel source from the manufacturer, which should be available if they are honoring the GPL license, and in the file
Find the line of code that says:
EXTRA_CFLAGS += -DCONFIG_ALWAYS_ENFORCE=true
and change the value of it to
false and recompile the kernel and make a zImage and flash it to boot.
That being said, TWRP should support SELinux Enforce, just never EVER run a