"...or downloading apps..."
I played this game in 2016 and it was possible to get plat by downloading apps. Here in 2018 I don't see the option to do that anymore. NativeX says "NativeX is not currently available." Supersonic ads says "Sorry but we have no available offers for you." Fyber is the only thing that pulls up, and none of them are downloading apps. All offers are for making purchases or completing surveys where the deceptive last step is to make a purchase.
In other words, there are no FREE plat offers anymore.
We’re reviewing alternatives to Supersonic and NativeX at the moment, if you’ve used other offerwalls in the past that you’ve liked and want to suggest I’m certainly open to taking a look.
As others have said purchasing chests from other players with gold is also a good way to get plat.
I'm not a shortcut to support, don't expect a reply to PMs asking about support issues.