How did you judge that Yield.app is one of the best platforms to do that when they just launched a few months ago? Btw those rates might change when more and more people enter the pool, resulting in a lot of capital stored without being utilized.
I think staking through a platform like Ledger is probably only possible if the chain/network itself allows delegated staking or something like a proof of lease. That being said, I do think it's way better compared to sending your money to a custodial entity for staking.
You are right, the Yield.app platform rates might change, but they plan to maintain the 20% for a longer time and it's highly likely that the rates will stay well above most competitors as up to 50% of the reward is paid in YLD tokens.
Now the YLD token might decrease in price but from my research so far it seems to have quite a lot of potential, similar to CEL which skyrocketed this year.
Yield.App and Anchor is my top alternatives so far, but I am definitely open for other suggestions.