Bonds is a popular asset class offered by several retail brokers, including some crypto brokers. Among long-term investors, bonds are often used in combination with stocks as a way to reduce risk and smooth out volatility in an investment portfolio. However, they can also be traded on shorter timeframes in the form of leveraged CFDs.
Most bonds that are offered by crypto & forex brokers are government-issued bonds from first-world countries like the US, Germany, and the UK. These are stable assets, and are usually considered among the safest investments that exist. As such, yields on these bonds are usually quite low, but this can be compensated by using highly leveraged CFDs.