Hello @Alexander Zhavoronkov ,
If I understand correctly, you are trying to migrate your linux VMs from Subscription A (Source) to Subscription B (Destination). If yes, then check out the steps outlined here.
You will need to disable encryption to move a linux VM integrated with Keyvault .
Review this content to learn more about current unsupported scenarios.
Dont hesitate to let me know if I misunderstood your question. Happy to followup.
Cheers.