Synology Update is available
Go to the Synology Download Center. Select your Synology NAS model from the product category and model drop-down menus. Scroll down to the middle section of the page, and click on the Operating System tab. Select your current DSM version and the version you'd like to update to.

But stuck at download and install

Manual Website Download
https://www.synology.com/en-us/support/download/DS918+?version=7.1#system


Loading > after a manual update


Fail

Reference
https://twitter.com/rifaterdemsahin/status/1670376138256924672