Creating VMs in other CSP AAD Tenancies from my VM Images in Azure

I am sorry if the question isn't so sharp or accurate but I am new to Azure, so feel free to ask for clarifications if needed.

I want to share a VM Image with other customers outside my organisation and AD. More precisely, we have a reseller relationship with them through CSP and I don't want to manually create the VM there every time, which entails installing and configuring a suite of applications.

I create a Shared Image Gallery and an Image Definition/Version. I shared the gallery with another user outside my organisation and under a different tenancy and AD. That user can read the image now, however, they cannot create a VM from the images in their subscription/directory but only in my organisation's directory/subscription.

How can I share an Image from my AAD to other AAD tenancies so that they can be created there? Azure Portal is preferred, but CLI is also OK.