In my region, using UDP only brings more drawbacks. How can I completely shut down UDP?
You can make node not listen on UDP port if you specify exiplicitly listen port and set it to TCP only, but you can’t prevent others from using UDP and potentially UDP only. As such there is no flag to disable UDP completely, it will fall back to TCP if necessary if connection via UDP is not possible to establish.
It would be helpful to know what drawbacks are you talking about specifically such that we can try to address them.