Simple rules as written question. Can a Druid who has a domain spell that is not on the druid spell list prepare that spell in a non domain spell slot? It is very clear that the answer is no with a Cleric, does this same rule apply to a Druid?
Correct, they could not prepare those spells in non-Domain slots, but just like a Cleric they would be free to use Spell Trigger and Spell Completion without the need for UMD.
However, note that the Storm Druid, Tempest Druid, and Urban Druid can all spontaneously cast domain spells instead of SNA, and you can prepare a lower level domain spell in a higher level domain slot.