Tempted to apply as a species of bug-trees where the 'land' on their world are essentially living islands. Able to merge their consciousness with the land, a terrible plague gutted their society at its height and has destroyed much of their ancestral knowledge.

Their overall tech-level is stagnant, but their governments - the 'Four Courts' - possess a small handful of hyper advanced relics.

In other words, aspect for aspect they're less advanced than most, but their leadership get dibs on a small but finite number of Really Awesome Things. Or to put it another way...

Joe-Average Bug Tree is a medieval peasant who uses various biological 'suits' to harvest the land and grow the islands in the hopes of eventually covering the surface of their globe and reclaim the damage caused by the plague. Superstitious and hungry, it works for its masters to protect its family and offer service to the pantheon and its ancestors.
The Courtly Masters, meanwhile, are the descendants of those untouched by the plague, still containing the genetic markers needed to control the remaining technology and thus 'chosen by the gods' to rule over the galaxy...

The ground forces are some combination of soldiers from Blame! and Attack on Titan; vehicles are organic tree armour and war-beasts; space-ships are few and far between but powerful and self-regenerative, literally growing as seed pods from a series of massive Star Trees engineered during the golden age. When the going gets real tough, the Courtly Masters merge their consciousness with the army, becoming a temporary hive-mind over every tree that isn't a person.