Is it true that I can run any Gramine container in the Phala cloud?

Hi Newbie here, trying to understand what is and what is not possible in Phala.

The docs I have seen, imply that any Docker image can be wrapped up as a Gramine Shielded Container.

Is it also true that a Phala host can instantiate any GSC guest?

If not, what are the limitations?

Could this Docker image be used: https://github.com/getumbrel/umbrel ?