This script lists the expiry dates of apps sideloaded onto an O365 SharePoint site, given the app name. Modified based on a script from https://docs.microsoft.com/en-us/sharepoint/dev/sp-add-ins/replace-an-expiring-client-secret-in-a-sharepoint-add-in to accept the name of a particular app and formatted a little more clearly.

ListSharePointSideLoadedAppExpiryDates.ps1

#This script lists the expiry dates of apps sideloaded onto an O365 SharePoint site, given the app name.
#Modified based on a script from https://docs.microsoft.com/en-us/sharepoint/dev/sp-add-ins/replace-an-expiring-client-secret-in-a-sharepoint-add-in
#to accept the name of a particular app and formatted a little more clearly. Prerequisites for running this app are listed at the link above.
Clear-Host
Connect-MsolService
$appName = Read-Host 'Partial name of your app?'
$applist = Get-MsolServicePrincipal -all  |Where-Object -FilterScript { ($_.DisplayName -like "*$appName*") -and ($_.DisplayName -notlike "*Microsoft*") -and ($_.DisplayName -notlike "autohost*") -and  ($_.ServicePrincipalNames -notlike "*localhost*") }

foreach ($appentry in $applist)
{
    $principalId = $appentry.AppPrincipalId
    $principalName = $appentry.DisplayName

    $date = get-date
    Write-Host "$principalName`n($principalId;$appentry.KeyId;$appentry.type;$date;$appentry.Usage)"
    Get-MsolServicePrincipalCredential -AppPrincipalId $principalId -ReturnKeyValues $false | Where-Object { ($_.Type -ne "Other") -and ($_.Type -ne "Asymmetric") }

}