Where is the best place to buy T-bills?

Inquiring minds want to know: Where precisely is the optimal venue to acquire Treasury bills, or T-bills, for optimal yield and security? With the volatile nature of financial markets, it's crucial to identify a trusted platform that offers both competitive interest rates and a robust security infrastructure. Could you elaborate on the key factors one should consider while searching for the best place to invest in T-bills? Is it a matter of choosing between traditional brick-and-mortar banks or exploring digital alternatives? Additionally, what are the potential risks involved, and how can investors mitigate them? Your insights would be invaluable for those seeking to navigate the world of T-bill investments.