Starting with Azure DevOps Server 2019 (formerly TFS), the Inheritance Process Model configuration is supported. This has been the default process used in Azure DevOps for quite some time now.
Upon creating a new collection in your Azure DevOps Server 2019 and newer, you will be asked to choose the process model for the new collection (see screenshot, below).
The main difference for 7pace Timetracker (and the end user) is that to add Work Item Contributions (the "Time" tab and "Start Tracking" button) for an XML-based collection, it is required to modify all Work Item types' XML and upload modified XML definitions back to DevOps server.
In the Inheritance Process Model, this is no longer required and supported, and extensions will work out-of-the-box after installation. In this case, the 7pace Configuration Tool will display a disabled checkbox on the "Installing Work Item Form Contributions" window:
To configure visibility in the inherited processes, you can navigate to Process Customization page and change visibility of Timetracker contributions (see details here: https://docs.microsoft.com/en-us/azure/devops/organizations/settings/work/custom-controls-process)