I guess I don't *know* know, but there's no real evidence besides the word of an ex-spy (and they have a habit of making all kinds of allegations for money), and the circumstantial evidence. But the latter is better explained by the ideological affnities between the two.
Comments
Line of attack two: Former KGB intelligence chief says Trump’s a KGB agent
https://www.marxists.org/reference/archive/liu-shaoqi/1952/internationalism_nationalism/ch01.htm