The best alternatives to DoubleTake are Pulpix, upclose, and VidGrid.tk.gg. If these 3 options don't work for you, we've listed a few more alternatives below.
VidGrid is a browser-based YouTube/m3u8 playlist viewer that recreates the view of a TV producer in the control room in your browser. Originally built for journalists to keep the newsroom-feel during the work-from-home COVID crisis.