[PTTG]

I'm liking that a lot. I myself would presume that the Lurjahrites were humans transported to an alien planet or worldline. But such details would be academic to the natives.

What sort of ideologies do the Lurjahrites have?

Here's a thought: Lurjahr was a long-abandoned gateway world built by an alien race. For tens of thousands of years, its gates sporadically opened onto all sorts of planets, bringing a constant influx of alien life-forms from across the galaxy. As a result, only the most hardy and adaptable survived (it turns out that water, carbon, and .2 atmospheres of oxygen is a fairly common basis for life). Humans, and some other Earth life, were the last to arrive before the stellar power plant shut down.

It took another four thousand years to reach something like TL8 (they were slowed by the many dangerous aliens of the planet and spurred on by the artifacts that surrounded them), which gave the Lurjahrites the understanding needed to figure out where they had come from and how to repair and the portal array. That it was already targeting Earth was a useful coincidence.

The result of all that is that a very large proportion of the aliens will be the exact sort that can be successful invasive species.

The odd thing is that the most deadly stuff will be the diseases that the humans brought with them that then mutated.