If you'd like to visit the Weisman in person, it's now reopened. Admission to the museum is free; open Thurs - Sun, noon - 5. Here are details about COVID precautions and changes to the visitor experience, from the museum's website: https://wam.umn.edu/visit/
Not sure about other museums, but I went to this one last weekend just fine, no reservation, just walk in
They are but some, like MIA, are having you get tickets before hand so they can keep track of how many people come and go
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