default or selected kernelversion does not have config value CONFIG_HISAX_NETJET_U.
Result is shown for kernelversion 6.9.9

NETspider U card

configname: CONFIG_HISAX_NETJET_U

Linux Kernel Configuration
└─>Device Drivers
└─>ISDN support
└─>Old ISDN4Linux (deprecated)
└─>Passive cards
└─>NETspider U card
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
This enables HiSax support for the Netspider U interface ISDN card
from Traverse Technologies.
See <file:Documentation/isdn/README.HiSax> on how to configure it
using a different D-channel protocol, or non-standard IRQ/port
settings.