I-CTS10228 corresponds with Thracian land and younger clades are Illyrians.
It is normal what correspond, not really northeast Europe, but of course today's Ukraine/Romania and beyond of with the North decreases (Southern-Eastern Poland, part of Belarus and small part of Russia).
What someones do not understand because they do not know, practically speaking, Slavs did not exist in the 3rd century BC.
Pan-Slavist nationalists and here in forum Albanian nationalists what is unbelievable combination (Albanians promote Pan-Slavism, LOL), think that cultures as Zarubintsy are Slavic but no, these cultures are not Slavic.
https://en.wikipedia.org/wiki/Zarubintsy_culture
The Zarubintsy culture was influenced by the La Tene culture and the nomads of the steppes (the Scytians and the Sarmatians). The Scythian and Sarmatian influence is evident, especially in potterty, weponry and domestic and personal objects. From the 3rd century and onwards, the culture was connected by the Goths and became part of the Chernyakov culture.
I-CTS10228 formed 5500 ybp, TMCRA according Klyosov and Nordtvedt is about 300 BC.
Slavs emerged later.
In third century BC we can speak about Thracians, Sarmatians, Scythians, Goths etc. but not about Slavs.
Objectively I-CTS10228 can be Thracian or German (Gothic) marker but a lack this haplogrup in some areas where Goths moved gives much greater priority of Thracian theory.
Younger clades as PH908 can be Illyrians.
If we analyze who is more Illyrian and Thracian among Balkan people we can see:
Croatians are mostly Illyrians, but in the Eastern parts are more Thracians
Bosnians are more Illyrians than Thracians
Serbs are both, Western Serbs are more Illyrians, Eastern Serbs are more Thracians
Bulgarian are mostly Thracians
Illyrians and Thracians in these area were mixed, and there are experts who claim language was not so different, even according them Illyrians and Thracians could understand each other.
