At least in Germany, especially here in the eastern part where right-wing radicalisation is very prevalent, the lack of adequate street-work (in this sense) and youth centres offers is discussed as a contributing factor. More generally/systemically, I’ve seen arguments that the sudden and wholesale disappearance of previous social structures that engaged youth[1] left the space open for neo-Nazi groups to basically be “the people who are there, who give us something to do and a reason to do it”.
As to what that kind of street-work looks like, even if not offered at nearly enough capacity, here’s an example. It ranges from organising leisure activities to helping kids who have trouble with the law - so that neo-nazis aren’t the ones who are the first to offer their help and win their trust.
[1]: Such as the Protestant Church and the state-controlled youth organisation of the GDR - reminder: what was previously keeping kids engaged doesn’t have to necessarily be good. Something bad can be replaced by something also bad. The point is to replace it by something good.