Falkon started properly with glibc-2.33.9000-43.fc35.x86_64. When glibc was upgraded to glibc-2.33.9000-50.fc35.x86_64 (missed out on the in-betweens), it would hang when trying to display the start page, falkon:start. The tab title, "falkon:start" and the throbber on the tab blink very quickly; the stop button has no effect. If I open a new (blank tab), the blinking text on the new tab is "data: text/html; charset=UTF-8,%3..."