Where is the best place to buy US treasuries?

Can you please provide some insights on the most suitable platform or avenue for acquiring US treasuries? Are there any specific exchanges, brokerages, or direct channels that are renowned for offering competitive rates, seamless transactions, and robust security measures? Also, are there any factors I should consider before making a decision, such as fees, market accessibility, or liquidity? Ultimately, I'm seeking guidance on the optimal location to invest in US treasuries, ensuring I get the best possible deal while mitigating risks.