Is it true: MH370: Deliberate Pilot Action Hypothesis?

There's no solid evidence for it.

The deliberate pilot action hypothesis is consistent with some evidence — the flight simulator waypoints, the sequential disabling of communications, and the ghost-flight trajectory — but is not supported by conclusive proof. No motive has been established, no suicide note or farewell communications were found, the simulator route reconstruction is partial and characterised as inconclusive by Malaysian authorities, and neither black box has been recovered. The ATSB and Malaysian investigation both declined to assign cause.