Oh, so who were in eastern europe before IE speaking people.
Nobody knows because by the time writing spread to that region of the world, the IE language families were generally already in the locations that we find them. There is no record of the languages which were previously spoken.
We can follow archaeological cultures further back in time, but no one truly knows how archaeological cultures correlate to any of the languages which might feasibly have existed in the area. And archaeological cultures are a different kind of culture than what people usually think of as a human culture… it only refers to a broad set of material artifacts. So an archaeological culture could easily span across numerous unrelated languages, or a single language might encompass several vastly different material cultural sets. There is simply no evidence connecting any languages to archaeology before writing was introduced to these areas.
Linguistically there might be a few inferences that could be made. The Germanic Substrate Hypothesis, for instance observes that there are numerous elements within the Germanic languages which don’t seem to be of IE origin. So it is speculated there must have been non IE speakers must have originally been living in the region were the Germanic languages developed. (
Germanic substrate hypothesis - Wikipedia) But it is a highly debated topic.
Also some Finno-Ugric languages in Central Asia, if I recall correctly, have several IE words in their lexicon which would have been borrowed from some Indo-Iranian languages, indicating that there must have been a zone of contact between those two language groups throughout that region. That’s about all I can think of.
