Culturally Europe is all about Real Estate and Bonds, that's what people are trained to think about it ever since they start approaching the world of investments in their 20s/30s. If I had to give a suggestion I'd say that although the term BogleHeads comes from Jack Bogle, the name of the institution is Vanguard which is an Asset Manager and provider of Mutual Funds
So maybe look if a similar culture developed around the long time clients of Asset Managers and providers of Mutual Funds/ETFs in Europe?
Legal&General, Aviva, UBS, Allianz, Amundi, BNP Paribas, Aegon, Naxitis, Generali Assicurazioni are among the largest in Europe according to the Thinking Ahead Insitute[0]
In general again the whole thought leadership thing doesn't find fertile ground in Europe (except for politics) and especially in the realm of business and investing even those who get to the very top don't feel the need to propagate their doctrine, unlike the U.S. In Europe the focus shifts on enjoying the money by again acquiring Real Estate, Football Clubs, Vineyards etc.
At the end of the day Jack Bogle, Graham etc. were thought leaders, everybody who writes a book positions themselves to become one, or at least aspires to be.
[0] https://www.thinkingaheadinstitute.org/news/article/top-500-...
https://www.bogleheads.org/forum/viewforum.php?f=22
2) Rational Reminder forum is general equity investing forum similar to Bogleheads and many of the active participants are Europe residents: