Street? I run Toyo Proxes S/T on my Suburban and like them alot. They are available in 275/55R20.
Off Road/AT? If you're willing to go a little bit taller (32.9 inches tall), Toyo Open Country A/T and Nitto Terra Grappler are available in 275/60R20. If you are willing to go a little wider, BFG makes their A/T in 285/55R20. Even wider still would be 305/55R20 from Toyo or Nitto.
Lots of choices... and lots of opinions and input from people here who run each type of tire. Good luck.
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