Any way to call a list within a map using lookup?

Terraform
1

I have this locals in my main.tf:

locals {
  inbound_interfaces = [
   {
    content_source_name     = "name1"
    content_source_role_arn = {}
    environment             = var.env_name == "qa" ? "stg" : var.env_name
    brand_portfolio         = "brand1"
   },
   {
    content_source_name     = "name2"
    content_source_role_arn = {
     sandbox = [
      "arn:aws:iam::account1:role",
      "arn:aws:iam::account2:role"
     ]
    }
    environment             = var.env_name == "qa" ? "stg" : var.env_name
    brand_portfolio         = "brand2"
   }
 ]
}

And in my permissions.tf, I’m setting up the role this way:

resource "aws_iam_role" "content_source_role" {
  count  = length(local.inbound_interfaces)
  name   = "CSRole_${local.inbound_interfaces[count.index].content_source_name}"

   assume_role_policy = <<EOF
  {
   "Version": "2012-10-17",
   "Statement": [
    {
     "Effect": "Allow",
     "Principal": {
       "AWS": "${lookup(local.inbound_interfaces[count.index].content_source_role_arn, var.env_name, "arn:aws:iam::account:role/temp_role")}"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}
EOF

But the lookup that “brings” the arn, fails because I guess it doesn’t expect a list but it expects a string in var.env_name

How can I call that list inside the inbound_interface -> content_source_role_arn, in the lookup, to take both roles and associate them to each role of each content_source?