How can I centrally manage Lenovo laptop updates without an on-premises server?

Lenovo System Update is another option. Install it on each machine and configure it to scan and apply Lenovo drivers, firmware, and BIOS updates. Lenovo also provides enterprise configuration options, so it can work well when combined with centralized Windows policies.

If you are already using NinjaOne, it may be worth reconsidering that approach. Lenovo updates that appear in Commercial Vantage can also be deployed through NinjaOne now, and a Lenovo-only fleet can be managed that way without adding another management platform. Commercial Vantage has some quirks, especially during provisioning, so test the workflow on a small group first.

Lenovo Commercial Vantage is probably the closest fit. It can manage Lenovo-specific updates and can be configured with policies and scheduled update behavior. Keep in mind that it is now distributed through the Microsoft Store, which can make it awkward to include in a generalized Windows image.

You could also use LSUClient with PowerShell. It queries Lenovo's update catalog and lets you script the installation of applicable updates, which makes it useful for scheduled deployment through an existing management tool or task scheduler.