LeStallion journals for fountain pens 3
https://wiki-triod.win/index.php/Finding_the_Best_Notebooks_for_Fountain_Pens_from_LeStallion:_A_Practical_Guide
I’ve been using LeStallion journals for fountain pens and they handle even wet nibs without bleed-through. The paper has a nice tooth that catches the ink just enough to make writing feel deliberate.