How to Get Last Reboot VM using Azure Graph Query

Indeed, that's why I said "the challenge with the graph is getting the time of the last action" - the majority of resources data doesn't have much other than created. If you only see created then that's all that is available.

This is much the same in Azure Monitor which will only have logs when the agent runs.

Now in a Workbook we can MERGE the two datasets, to get the answer.

This is an example Workbook I did a while ago that shows that (it merges the results from ARG with a Logs Query in KQL)

https://raw.githubusercontent.com/clivewatson/KQLpublic/master/KQL/Workbooks/findMissingComputers/findComputersMissingInLogs%20v0.2.workbook

So I now see in my Use Case - I'm showing All machines that ARG knows have been created but have never been started to log any data in the past 90days.