For me, jury's still out on Lindelof. He's had a good run for maybe half a season. Pretty much every one of our CBs has had a purple patch for longer than that - remember when Rojones was a thing?
If you require a Utd captain to be actually good in their role on the pitch, then De Gea is the only logical choice (or maybe not after last season). If it's a dressing room / squad influence / leadership thing (Rooney was pretty influential in the dressing room for several years after his performances on the pitch turned to shit), I don't think there's anyone in the current squad who can be a good captain. Maybe Pogba if we can convince him to stay and not flirt with RM.