Most portable generators is vov configured and is not allowed to be connected to db board if not changed according to Sans.

The changes that needs to be done.
Use an earth electrode and connect the generator earth point to the earth electrode with a proper earth cable.
Use the same earth as your supply earth from the portable generator to the changeover switch and distribution board.
Also connect the earth of the earth rod to the supplier’s earth (same potential).
Bridge out the neutral and the earth at the generator to have the neutral as close as possible to 0 V, in accordance with SANS 10292. The mts needs to have a separate RCD or connected to db main Rcd with mains power light indication and generator light indication.