The scepter will not depart from Judah, nor the ruler's staff from between his feet
The "scepter" and the "staff" are long decorated sticks that kings carried. Here they are metonymies that stand for the power to rule. And, "Judah" stands for his descendants. AT: "The power to rule will always be with the descendants of Judah" (See: rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/figs-parallelism)
until Shiloh comes. The nations will obey him
Possible meanings are 1) "Shiloh" means "tribute." AT: "until the nations obey him and bring him tribute" or 2) "Shiloh" refers to the city of Shiloh. AT: "until the ruler comes to Shiloh. Then the nations will obey him." Many people consider this a prophecy about the Messiah who is a descendant of King David. David is a descendant of Judah.
The nations will obey him
Here "nations" refer to the people. AT: "The people of the nations will obey him" (See: rc://en/ta/man/translate/figs-metonymy)