Firstly, if you're planning on buying DEC on ethereum, just don't. In fact don't interact with ethereum at all. It's for the best, trust me.
Secondly, if like me, you make stupid mistakes and buy it on ethereum and on your wallet, I have learnt 2 things for you: moving that DEC to splinterlands will absolutely demolish you, and how to link trust wallet to your splinterlands account.
You need to get a metamask browser extension. Then import trust wallet using your seed phrase and https://iancoleman.io/bip39/ to convert the seed phrase into a private key. Once imported into metamask, go back into splinterlands and add the ethereum wallet itself directly. To claim the SPS, you have to click claim once the metamask has trust wallet imported (and the broswer is refreshed), and it'll prompt the metamask open once you click claim. Then you can claim your SPS rewards.
Your DEC is stuck forever.
To hell with ethereum. The only reason the price goes up is cause people are stuck on it or they're buying more to get off it.