In-motion use is supported for users with Starlink RV service meeting the following criteria:

Using Flat High Performance Starlink

Starlink is securely installed with the Wedge mount included with the Flat High Performance Starlink kit.

Using Flat High Performance Starlink while in-motion without the Wedge mount, or using any other Starlink model will void the limited warranty of your Starlink. 

https://www.theverge.com/2022/10/25/23423755/spacex-starlink-for-rvs-moving-vehicles-flat-high-performance