default or selected kernelversion does not have config value CONFIG_ATM.
Result is shown for kernelversion 5.9.9

Asynchronous Transfer Mode (ATM)

modulename: atm.ko
configname: CONFIG_ATM

Linux Kernel Configuration
└─> Networking support
└─> Networking options
└─> Asynchronous Transfer Mode (ATM)

ATM is a high-speed networking technology for Local Area Networks
and Wide Area Networks. It uses a fixed packet size and is
connection oriented, allowing for the negotiation of minimum
bandwidth requirements.

In order to participate in an ATM network, your Linux box needs an
ATM networking card. If you have that, say Y here and to the driver
of your ATM card below.

Note that you need a set of user-space programs to actually make use
of ATM. See the file <file:Documentation/networking/atm.rst> for
further details.

source code: