You should have a variable on the Character Blueprint as the AnimBP reads from the character.
So for example when you equip a new weapon have the server set this variable on the character and replicate it to the client.
(Maybe it’s an enum of weapon types, so like “Unarmed, Pistol, Rifle” and the value gets set each time a weapon is equipped/unequipped.)
Then the AnimBP can read this from the character and store this variable and then you can use that to choose the anim state during your animbp anim graph logic.