Steps through all Azure SQLDB Servers and databases to find user-specific index usage

Find-UnusedDatabases.ps1

import-module az.sql
import-module az.resources
import-module importexcel

# Update-AzConfig -DisplayBreakingChangeWarning $false

# sign in to Azure account
Connect-AzAccount

#Folder containing sql script and place to create Excel file
$sourceFolder = "C:\SourceCode\AzureSQLDB UnusedDatabases\"
$ExcelFile = $sourceFolder + "DatabaseUsage.xlsx"
Remove-Item $ExcelFile -ErrorAction SilentlyContinue

$query = Get-Content ($sourceFolder + "User_Index_Usage.sql") -Raw

#Get Access Token to connect to SQL Servers
$AccessToken = (Get-AzAccessToken -ResourceUrl https://database.windows.net).Token

#get current resource groups
$rg = Get-AzResourceGroup

foreach ($rgname in $rg.ResourceGroupName) {
  $servers = Get-AzSqlServer -ResourceGroupName $rgname

    foreach ($servername in $servers.ServerName) {
        #work with each database
        $databases = Get-AzSqlDatabase -ResourceGroupName $rgname -ServerName $servername | Where-Object DatabaseName -ne "master"

        foreach ($db in $databases.DatabaseName) {
            $params = @{
                'database' = $db
                'serverInstance' =  $servername + ".database.windows.net"
                'AccessToken' = $AccessToken
                'outputSqlErrors' = $true
                'query' = $query
                'EncryptConnection' = $true
              }
              $output = Invoke-SqlCmd @params -OutputAs DataRows
              
              ##May need to trim the worksheetname to something shorter if that will be referenced.
              $output | Export-Excel -Path $ExcelFile -WorksheetName $servername -Append `
              -ExcludeProperty @("ItemArray", "RowError", "RowState", "Table", "HasErrors") -AutoSize -AutoFilter -BoldTopRow

        } #databases
    } #servers

} #Resource Groups

user_index_usage.sql

select * FROM (
SELECT @@servername as ServerName, db_name() as DatabaseName, '' as ObjectName, '' as IndexName, 0 as IndexID, 0 as UserSeeks, 0 as UserScans, 0 as UserLookups, 0 as UserUpdates, 0 as TableRows
UNION
SELECT
@@servername as ServerName
, db_name() as DatabaseName
, o.name AS ObjectName
, i.name AS IndexName
, i.index_id AS IndexID
, dm_ius.user_seeks AS UserSeeks
, dm_ius.user_scans AS UserScans
, dm_ius.user_lookups AS UserLookups
, dm_ius.user_updates AS UserUpdates
, p.TableRows
FROM sys.dm_db_index_usage_stats dm_ius
INNER JOIN sys.indexes i ON i.index_id = dm_ius.index_id 
AND dm_ius.OBJECT_ID = i.OBJECT_ID
INNER JOIN sys.objects o ON dm_ius.OBJECT_ID = o.OBJECT_ID
INNER JOIN sys.schemas s ON o.schema_id = s.schema_id
INNER JOIN (SELECT SUM(p.rows) TableRows, p.index_id, p.OBJECT_ID
FROM sys.partitions p GROUP BY p.index_id, p.OBJECT_ID) p
ON p.index_id = dm_ius.index_id AND dm_ius.OBJECT_ID = p.OBJECT_ID
WHERE OBJECTPROPERTY(dm_ius.OBJECT_ID,'IsUserTable') = 1
AND dm_ius.database_id = DB_ID()
AND i.type_desc = 'nonclustered'
AND i.is_primary_key = 0
AND i.is_unique_constraint = 0
and NOT (user_lookups = 0 and user_scans = 0 and user_seeks = 0 and user_updates = 0)
) as t

ORDER BY UserSeeks + UserScans + UserLookups ASC
GO

With thanks to Pinal Dave for the Index query.