lightdm: still needed for some UIs?

What's the current behaviour?

With i3wm chosen on the N900, it appears there are two display managers running, both lightdm (which the i3wm package depends on) and tinydm (which the postmarketos-base-ui package depends on). Although the device works properly with this situation, I guess we can save a few MB of RAM by running only one of them.

What's the expected behaviour?

One display manager should be running

it seems i3wm, mate, and xfce4 are the ones that depend on lightdm. i suppose this needs to be changed. at least i3wm starts fine with tinydm on my device