default or selected kernelversion does not have config value CONFIG_NET_SCH_ATM.
Result is shown for kernelversion 6.7.6

ATM Virtual Circuits (ATM)

modulename: sch_atm.ko

configname: CONFIG_NET_SCH_ATM

Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>QoS and/or fair queueing
└─>ATM Virtual Circuits (ATM)
In linux kernel since version 2.6.12  
Say Y here if you want to use the ATM pseudo-scheduler. This
provides a framework for invoking classifiers, which in turn
select classes of this queuing discipline. Each class maps
the flow(s) it is handling to a given virtual circuit.

See the top of <file:net/sched/sch_atm.c> for more details.

To compile this code as a module, choose M here: the
module will be called sch_atm.

source code: