Manufactured home water heater venting and gas line

Anybody know the requirements for exhaust venting a water heater in a manufactured home? Is it the same configuration as a regular home?
Is a flexible gas line ok or should it be hard piped?

Vented out the roof using a properly rated vent. Yes, flexible connector from Hardline shutoff to appliance is ok.

MH’s typically are direct vent vs. a conventional draft one you normally see.