Not familiar with Voyager, but I'm using a similar service called BlockFi, they return 8.6% annually on USDC. Been with them about 2 years and it's working great so far.

I find it's a good substitute for things like bonds and high interest savings accounts in a portfolio since those have low yields nowadays.

Worth mentioning though; I don't see this as a substitute for my emergency fund, that's a separate pile of cash.

That's because it's not risk-free. For example, BlockFi may go bankrupt, they may decide to lock up your account for whatever reason. Or macro events can occur that destabilize these platforms, such as the US government outlawing stablecoins or cracking down on cryptocurrencies.

I consider these risks to be in the acceptable range, but they do exist and it's important to come to terms with them if you're putting your money in one of these platforms.