Is It Possible to Encrypt varbinary(max) Column Using Always Encrypted Feature?
The limitations are listed here and do not mention VARBINARY(MAX).

https://docs.microsoft.com/en-us/sql/relational-databases/security/encryption/always-encrypted-database-engine

The way to do this when the feature first came out was: 

https://justdaveinfo.wordpress.com/category/always-encrypted/  


  Disclosure
  I am the author of the above blog


It is easier now though either via: 


SSMS https://docs.microsoft.com/en-us/sql/relational-databases/security/encryption/configure-always-encrypted-using-sql-server-management-studio
Powershell https://docs.microsoft.com/en-us/sql/relational-databases/security/encryption/configure-always-encrypted-using-powershell