Hello Luis,
Welcome to the Microsoft Community Forums. Have you taken a look at Azure Virtual Desktop Insights? Azure Virtual Desktop Insights you can use Azure Monitor to track logon times. Insights measure the time for a desktop experience to launch based on how long it takes to launch Windows Explorer. For RemoteApp, it measures the time taken to launch the first instance of the shell app for a connection. To set this up you can review: Enable Insights to monitor Azure Virtual Desktop | Microsoft Learn.
Once you have that configured you could use Log Analytics to capture log analytics for when users log in and out of Azure Virtual Desktops. You might need to create your own workbook or find one that someone else has created to visualize this information.