On KDE the cursor shape aspect doesn't match macOS (in the sense that if it's showing a resize cursor, it'll resize the window, no matter what), but per my comment further up the chain it'll absolutely work if it's just a normal cursor but between the handle and the edge of the window. Tried it on both Firefox and Konsole (which are subtly different due to Gtk v. Qt quirkiness but have the same behavior).

Though I'm using click-to-focus, not focus-follows-mouse, so YMMV.