Disable immobiliser

Hello Have now for a few days my 98er Legacy GL 2.0 Aut. Now I’m just playing around, preparing and waiting…brake system completely new, transmission and diff oils etc. I’m totally happy with the vehicle. The only disturbing thing, but the Legacy can’t do anything about it, is that I just got a key to the vehicle. Would like to have 2 reworked. Unfortunately, the plate with the key number did not have. Since I don’t need the immobilizer anyway, I would like to Is there a possibility without or can he deactivate it at all? Greeting Andi