I’m currently writing an application that uses virtual lists in GTK: GtkListView, GtkGridView, there may be others. You ruled out GTK because of its looks I guess, I’m targeting Linux so the looks are perfect.

Yeah, I need cross platform, and GTK looks quite foreign on Windows/macOS IMO. I toyed with custom themes, but couldn't find any I liked for a cross platform look (wanted something closer to Fluent UI).