When running the command "show ethernet-switching table" I receive an error.

"error: the l2-learning subsystem is not running"

Manually started the l2ald process, and then when running the command the cli hangs, returning no output.

error: the l2-learning subsystem is not running

The l2-learning process is not enabled when we dont have l2 config on device, which access switching table.

l2vpn or l2circuit will not have mac-learning, as they are p2p & hence l2-learning is not enabled with availability of these config in device.

Evpn/vpls/vlans are typical layer 2 with flooding/mac learning requirement, thus l2ald (l2-learning) process will be created once we have config for any of these.