Stellaris has simultaneously received both a large update and a new paid DLC today. The update contains a whole swath of bug fixes and some larger mechanics changes to accommodate the DLC. So you'll still benefit from most of the changes, even if you're not interested in the expansion. On top of that it's time retire that 32-bit hardware as Stellaris is now a 64-bit application.
The Ancient Relics DLC is all about archeology and discovering the remains of forgone civilizations. Two in particular, the Baol and the Zroni, have significant lore for you to discover. Additionally, unearthed artifacts using the new relics system can grant your empire significant bonuses for your own escapades.
Stellaris Ancient Relics is available on
Steam.