System boots without error, lightdm.service works.
When I log out, the lightdm greeter screen (which allows to select users and graphical environment) does not appear, the system returns to the desktop. There is no such problem when using gdm3.
It maybe an issue from lightdm itself. In that case, we can only try to upgrade the lightdm version in future. This will not happen soon. Thus, I would suggest you can still try to use gdm3 or try to configure lightdm by yourself first.