Slavic Native Faith in Poland
The Slavic Native Faith in Poland (Rodnovery; Polish: Rodzimowierstwo) has, in 2007, between 2000 and 2500 "actively engaged and regular participants". In 2020, Konrad Kośnik and Elżbieta Hornowska estimated that Rodnovers in Poland were between 7000 and 10,000.
Source: Wikipedia — Slavic Native Faith in Poland (CC BY-SA 4.0)