It seems that mouse acceleration cannot be disabled when Enlightenment is used with Wayland.
Acceleration is set to 1 (minimum possible) in Settings -> Input -> Mouse but mouse is still heavily accelerated.
On X11, acceleration can be disabled. Note: I'm not sure about the Mouse options in the Settings panel; I use xorg.conf for this. But xorg.conf is only for X11, not Wayland.
OS is Arch Linux x86-64 and Enlightenment main package version is 0.22.4-1.