We can use the $data property to repeat elements using an array of data, this is documented in the below Microsoft Docs page under the section Repeating items in an array.
https://docs.microsoft.com/en-us/adaptive-cards/templating/language#repeating-items-in-an-array
Given the following template and sample test data, a FactSet is used to render the displayName and userPrincipalName which has an array of User objects bound to the $data property of the FactSet object.
The preview does not render the list or values.

It is however correctly rendered in the AdaptiveCards.io designer when the Preview Mode is enabled.

I am suggesting that this is a bug due to the answer from @DeeJayTC on the below StackOverflow post which suggests that rendering of array bound elements is possible.
If you need a design time experience for array bound elements you can use Adaptive Cards Studio the Visual Studio Code Extension for card authoring.
https://stackoverflow.com/a/63233919/4871999
Template
{
"$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
"type": "AdaptiveCard",
"version": "1.4",
"body": [
{
"type": "FactSet",
"facts": [
{
"$data": "${users}",
"title": "${displayName}:",
"value": "${userPrincipalName}"
}
]
}
]
}
Data
{
"users": [
{
"displayName": "Lidia Holloway",
"userPrincipalName": "LidiaH@contoso.OnMicrosoft.com"
},
{
"displayName": "MOD Administrator",
"userPrincipalName": "admin@contoso.onmicrosoft.com"
},
{
"displayName": "Isaiah Langer",
"userPrincipalName": "IsaiahL@contoso.OnMicrosoft.com"
}
]
}
We can use the
$dataproperty to repeat elements using an array of data, this is documented in the below Microsoft Docs page under the sectionRepeating items in an array.https://docs.microsoft.com/en-us/adaptive-cards/templating/language#repeating-items-in-an-array
Given the following template and sample test data, a
FactSetis used to render thedisplayNameanduserPrincipalNamewhich has an array ofUserobjects bound to the$dataproperty of theFactSetobject.The preview does not render the list or values.
It is however correctly rendered in the AdaptiveCards.io designer when the Preview Mode is enabled.
I am suggesting that this is a bug due to the answer from @DeeJayTC on the below StackOverflow post which suggests that rendering of array bound elements is possible.
https://stackoverflow.com/a/63233919/4871999
Template
{ "$schema": "http://adaptivecards.io/schemas/adaptive-card.json", "type": "AdaptiveCard", "version": "1.4", "body": [ { "type": "FactSet", "facts": [ { "$data": "${users}", "title": "${displayName}:", "value": "${userPrincipalName}" } ] } ] }Data
{ "users": [ { "displayName": "Lidia Holloway", "userPrincipalName": "LidiaH@contoso.OnMicrosoft.com" }, { "displayName": "MOD Administrator", "userPrincipalName": "admin@contoso.onmicrosoft.com" }, { "displayName": "Isaiah Langer", "userPrincipalName": "IsaiahL@contoso.OnMicrosoft.com" } ] }