Fortnite on two devices?

Can you play on two different devices on the same Fortnite account or is it forbidden?

You can play on different devices with the same account, but not at the same time. And it is pretty safe allowed, after all, the devices are constantly being developed and so you will also change the device.

Is allowed.

But as others said, not at the same time, but note that V-Bucks is not platform transferred, means you only have the V-Bucks on one device although the same account and if you now play on another you do not have the V-Bucks