What "managed" does not mean
Managed does not mean we write your content, configure your business rules or train your users. We run the machine and the software; the use of it stays yours.
Managed does not mean "anything is possible" either. You have no SSH access and you cannot install an arbitrary module inside the container. That is the price of isolation and stability — and it is also what makes guaranteed updates possible.
If you want your own docker-compose, software outside the catalogue or root access, the right product is not this one but a VPS. The page managed applications or a VPS sets out exactly where the line falls.