Backup logs at Tools & Settings > Backup Manager show the below warning message:
Warning: Extension "Laravel Toolkit"
Unable to back up extension. Error: Failed to exec backup_restore_helper: Exit code: 1
#EXTPLESK-3725 "No longer causes backup to show warnings for domains without Laravel ."
- Laravel Toolkit 1.2.2 05 July 2022
If an update is not possible for some reason you may try the following
For the domains that don't have the Laravel installed the warnings can be safely ignored, it won't affect the backup.