default or selected kernelversion does not have config value CONFIG_BT_L2CAP_EXT_FEATURES.
Result is shown for kernelversion 5.4.229
L2CAP Extended Features support (EXPERIMENTAL)
configname: CONFIG_BT_L2CAP_EXT_FEATURES
Linux Kernel Configuration
└─>Networking support
└─>L2CAP Extended Features support (EXPERIMENTAL)
In linux kernel since version 2.6.35 (release Date: 2010-08-01)
This option enables the L2CAP Extended Features support. These
new features include the Enhanced Retransmission and Streaming
Modes, the Frame Check Sequence (FCS), and Segmentation and
Reassembly (SAR) for L2CAP packets. They are a required for the
new Alternate MAC/PHY and the Bluetooth Medical Profile.
You should say N unless you know what you are doing. Note that
this is in an experimental state yet.
new features include the Enhanced Retransmission and Streaming
Modes, the Frame Check Sequence (FCS), and Segmentation and
Reassembly (SAR) for L2CAP packets. They are a required for the
new Alternate MAC/PHY and the Bluetooth Medical Profile.
You should say N unless you know what you are doing. Note that
this is in an experimental state yet.