I suspect you are using an older version of TextMesh Pro as LateUpdate has been replaced by an UpdateManager.
I would be curious to see the performance differences between those. All newer version require the use of Unity 2018.3 or newer and available via the package manager.
If you are using a Legacy release of TextMesh Pro (Asset Store), you will need to migrate to the newer package manager releases and use the Project GUID Remapping Tool to convert the project over to the new format. Please be sure to follow the instructions in this sticky post .