How to update VMTemplate attribute of HostPool

Abel EspinoI don't think there is a way to change the VMtemplate (image) for a host pool.  You'll have to create a new host pool in the workspace using a different image.

In future I'd recommend saving your images in an Azure Share Image Gallery (https://docs.microsoft.com/en-us/azure/virtual-machines/windows/shared-image-galleries).  An image in a SIG is versioned and the host pool always uses the latest version.  So to update the session hosts in your host pool you update your image, save it as a new version of the image already in the SIG, then deploy new session hosts and finally drain and remove from the host pool the old session hosts.