In a world with deep subglacial seas and access to a rocky core rich in minerals with a large size (this world is a "super Europa" in orbit of a brown dwarf) a ancient, extremely biodiverse ecosystem has developed (for reasons akin to the biodiversity you see in say, rainforests; the inhabitable parts of the world are extremely populated in chemotrophic "trees" that without concern for gravity sprout from each other in a maze-like web that covers the deep surface of this world).
In this web-like forest of tubular plants, vibrant and diverse life forms who live in kilometers deep oceans exist in a environment where there is no light from the sun. Outside influences come only from the worlds around the planet in the form of tidal stress and the extremely rare comet that penetrates the shell (that would only happen on geolgical time scales).
A sapient species develops a form of advanced aquaculture, makes complex social structures and very recognizable civilizations on this world over thousands of years, developing to ever further levels of advancement down paths alien to our own. The environment is simply too different for them to develop in a way that is anything like Earth's. For example their tech would find methods of using vents and body heat to meld complex devices and various sorts of cellular systems that fill a computer-like niche. I am not sure how plausible any of this is. The premise is predicated on there being A. organic material in great abundance (due to having a ancient and complex biosphere) and B, a strong hydrothermal energy source with a mineral rich core to mine.
I believe it'd be unlikely that they'd become space faring simply because of the barriers a 12 km deep shell, radiation poisoning and frigid space have. It'd be a harder barrier to cross for them than going to space is for us because they live in much denser media than we do and we have to deal with a fair amount less radiation that they would. (Van Allen belts around dense gas giants are a pain from my understanding)
However, could these natives in spite of all that potentially be aware of their place in the universe through some other means, even if they can't get direct observation? How advanced could a sub-glacial alien civilization get until they get aware of outer space and attempt to explore it for other habitable worlds? What technological threshold may cause this and would such threshold need to be crossed in order for them not to be technologically outmatched by a human-like society?
I ask this question since I ideally want to have a situation where a interstellar society with less advanced technology opens a pandora's box by making a ancient, technologically superior but world-bound species aware of a whole universe far vaster than anything they ever imagined before and all the chaos that would ensue from that. Problem is I'm not too sure if there is any potential technologies they may develop along the way that would make them very aware of the outside universe and eventually have a culture that decides to see what's out there.
Culture is not being taken into account as much since this technology might not nessecarily be a technology dilliberately looking for anything outside their world, the discovery could be a completely unintentional result of said technology, for whatever reason it was developed. For instance in the cold war pulsar stars were discovered completely by accident.