Reports sandbox solution references in the farm.

Get-SandboxSolutionInstances.ps1

Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue | Out-Null

$sites = Get-SPSite -Limit All | ? IsReadLocked -eq $false

$results = @()

foreach( $site in $sites )
{
    $solutions = @($site | Get-SPUserSolution)

    if( $solutions.Count -gt 0 )
    {
        foreach( $solution in $solutions )
        {
            $results += [PSCUstomObject] @{
                            Site           = $site.Url
                            Name          = $solution.Name
                            Status        = $solution.Status
                            HasAssemblies = $solution.HasAssemblies
                        }
        }
    }
}

$results | Export-Csv -Path "SandboxSolutions.csv" -NoTypeInformation