Currently, there is no way to manually force a manual update to your device. Currently all firmware updates happen automatically.

Automatic Updates

Available updates will be downloaded and installed automatically, there are no sound and no indication through this process. The schedule time for the updates is between 00:00 am and 12:00 pm.

Updates via WiiM Home App

The App would automatically check the available updates and display the updates for you. 

You can check the WiiM Mini release notes in WiiM Home app or visit the WiiM Home website.