You probably want to consider live streaming the event which means using something with clean HDMI out or a USB webcam mode, along with a dedicated capture device/computer. At that point you can just dump a recording of any size to disk.
Fwiw, Sony's current mid-to-high end a7 line of mirrorless cameras (eg: the a7 IV) don't have this video recording limit. They also handle long recordings fine assuming it's on a tripod and screen is in the flipped out position[1] (the link ran a capture at 4K/60fps for 3 hours before ending the test arbitrarily).