GitHub documentation versus actual cmdlet

UDCard does support -Header and -Footer. You may be trying to mix parameter sets.

This is an example from the live does. You can view it in your own environment by visiting: http://localhost:5000/apps/docs/Card

$Header = New-UDCardHeader -Avatar (New-UDAvatar -Content { "R" } -Sx @{ backgroundColor = "#f44336" }) -Action (New-UDIconButton -Icon (New-UDIcon -Icon 'EllipsisVertical')) -Title 'Shrimp and Chorizo Paella' -SubHeader 'September 14, 2016';
     $Media = New-UDCardMedia -Image 'https://mui.com/static/images/cards/paella.jpg'
     $Body = New-UDCardBody -Content {
         New-UDTypography -Text ' This impressive paella is a perfect party dish and a fun meal to cook together with your guests. Add 1 cup of frozen peas along with the mussels, if you like.' -Sx @{
             color = 'text.secondary'
         } -Variant body2
     }
     $Footer = New-UDCardFooter -Content {
         New-UDIconButton -Icon (New-UDIcon -Icon 'Heart')
         New-UDIconButton -Icon (New-UDIcon -Icon 'ShareAlt')
     }
     $Expand = New-UDCardExpand -Content {
         $Description = "Heat oil in a (14- to 16-inch) paella pan or a large, deep skillet over medium-high heat. Add chicken, shrimp and chorizo, and cook, stirring occasionally until lightly browned, 6 to 8 minutes. Transfer shrimp to a large plate and set aside, leaving chicken and chorizo in the pan. Add pimentón, bay leaves, garlic, tomatoes, onion, salt and pepper, and cook, stirring often until thickened and fragrant, about 10 minutes. Add saffron broth and remaining 4 1/2 cups chicken broth; bring to a boil."
         New-UDTypography -Text $Description
     }
     New-UDCard -Header $Header -Media $Media -Body $Body -Footer $Footer -Expand $Expand -Sx @{
         maxWidth = 345
         border   = '2px solid #f0f2f5'
     } -Id 'card5'

You are right. I must have just had parenthesis mismatched.