Prior to nRF Connect SDK v2.6.0, the SoftDevice Controller, which is the Controller part of the BLE stack, did not support all features neaded for LE Audio. Therefore, prior to nRF Connect SDK v2.6.0, another BLE Controller was used, which supported the required features for implementing Bluetooth LE Audio on top. This Bluetooth LE controller is sometimes referred to as "LE Audio controller", such as e.g. in migration guides.
To elaborate, "LE Audio Controller" in this context is the same as "LE Audio-specific Controller subsystem" in the Bluetooth DNs and QDIDs table. In other words, a BLE Controller, which is part of the BLE stack, and with the capabilities for running Bluetooth LE Audio on top.
If you see "Audio controller" referenced (without "LE" in front), then please let us know and we can have a look and see if ti should be the same, or if it refers to some other concept.
