The same situation here, issue not fixed yet in 0.84.2. In version 82.1 my Xiao mi WXKG02LM AQARA Smart switch still works fine.
In 0.84.2 the sensors below are registered and visible on the dev-stat page in the GUI, but their state remain off
no matter I push one or both buttons.
binary_sensor.wall_switch_left_158d00xxxxxxxx
binary_sensor.wall_switch_right_158d00xxxxxxxx
binary_sensor.wall_switch_both_158d00xxxxxxxx
My other Xiaomi sensors (like below) work just fine in 0.83.x and 0.84.x:
binary_sensor.motion_sensor_158d000xxxxxxxx
sensor.temperature_158d000xxxxxxxx
sensor.pressure_158d000xxxxxxxx
sensor.humidity_158d000xxxxxxxx
Edit:
Down here my xiaomi debug logging.
dec 17 07:08:44 nuc.bachstraat20 docker[12783]: 2018-12-17 07:08:44 DEBUG (SyncWorker_12) [homeassistant.components.xiaomi_aqara] Expecting 1 gateways
dec 17 07:08:44 nuc.bachstraat20 docker[12783]: 2018-12-17 07:08:44 INFO (SyncWorker_12) [homeassistant.components.xiaomi_aqara] Discovering Xiaomi Gateways (Try 1)
dec 17 07:08:50 nuc.bachstraat20 docker[12783]: 2018-12-17 07:08:50 DEBUG (SyncWorker_12) [homeassistant.components.xiaomi_aqara] Gateways discovered. Listening for broadcasts
dec 17 07:09:14 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:14 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Temperature_158d000xxxxxxx: 18.4>: {'voltage': 2975, 'temperature': '1839', 'humidity': '5412', 'pressure': '100955'}
dec 17 07:09:14 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:14 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Humidity_158d000xxxxxxx: 54.1>: {'voltage': 2975, 'temperature': '1839', 'humidity': '5412', 'pressure': '100955'}
dec 17 07:09:14 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:14 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Pressure_158d000xxxxxxx: 1009.5>: {'voltage': 2975, 'temperature': '1839', 'humidity': '5412', 'pressure': '100955'}
dec 17 07:09:21 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:21 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Plug_158d000xxxxxxx: on>: {'voltage': 3600, 'status': 'on', 'inuse': '1', 'power_consumed': '1484', 'load_power': '1.66'}
dec 17 07:09:36 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:36 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Motion Sensor_158d000xxxxxxx: off>: {'lux': '4'}
dec 17 07:09:36 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:36 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Illumination_158d000xxxxxxx: 4.0>: {'lux': '4'}
dec 17 07:09:36 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:36 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Motion Sensor_158d000xxxxxxx: off>: {'status': 'motion'}
dec 17 07:09:36 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:36 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Illumination_158d000xxxxxxx: 4.0>: {'status': 'motion'}
dec 17 07:09:41 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:41 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Humidity_158d000xxxxxxx: 52.2>: {'temperature': '2070'}
dec 17 07:09:41 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:41 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Temperature_158d000xxxxxxx: 20.5>: {'temperature': '2070'}
dec 17 07:09:41 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:41 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Pressure_158d000xxxxxxx: 1009.7>: {'temperature': '2070'}
dec 17 07:09:41 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:41 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Humidity_158d000xxxxxxx: 52.2>: {'humidity': '5149'}
dec 17 07:09:41 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:41 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Temperature_158d000xxxxxxx: 20.7>: {'humidity': '5149'}
dec 17 07:09:41 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:41 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Pressure_158d000xxxxxxx: 1009.7>: {'humidity': '5149'}
dec 17 07:09:41 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:41 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Humidity_158d000xxxxxxx: 51.5>: {'pressure': '100975'}
dec 17 07:09:41 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:41 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Temperature_158d000xxxxxxx: 20.7>: {'pressure': '100975'}
dec 17 07:09:41 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:41 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Pressure_158d000xxxxxxx: 1009.7>: {'pressure': '100975'}
dec 17 07:09:41 nuc.bachstraat20 docker[12783]: 2018-12-17 07:09:41 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Humidity_158d000xxxxxxx: 51.5>: {'voltage': 2985, 'temperature': '2070', 'humidity': '5149', 'pressure': '100975'}
dec 17 07:10:28 nuc.bachstraat20 docker[12783]: 2018-12-17 07:10:28 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Humidity_158d000xxxxxxx: 64.2>: {'voltage': 2975, 'temperature': '1796', 'humidity': '6423', 'pressure': '101025'}
dec 17 07:10:28 nuc.bachstraat20 docker[12783]: 2018-12-17 07:10:28 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Pressure_158d000xxxxxxx: 1010.2>: {'voltage': 2975, 'temperature': '1796', 'humidity': '6423', 'pressure': '101025'}
dec 17 07:10:36 nuc.bachstraat20 docker[12783]: 2018-12-17 07:10:36 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Wall Switch (Left)_158d000xxxxxxx: off>: {'channel_0': 'click'}
dec 17 07:10:36 nuc.bachstraat20 docker[12783]: 2018-12-17 07:10:36 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Wall Switch (Both)_158d000xxxxxxx: off>: {'channel_0': 'click'}
dec 17 07:10:36 nuc.bachstraat20 docker[12783]: 2018-12-17 07:10:36 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Wall Switch (Right)_158d000xxxxxxx: off>: {'channel_0': 'click'}
dec 17 07:10:43 nuc.bachstraat20 docker[12783]: 2018-12-17 07:10:43 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Wall Switch (Left)_158d000xxxxxxx: off>: {'channel_1': 'click'}
dec 17 07:10:43 nuc.bachstraat20 docker[12783]: 2018-12-17 07:10:43 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Wall Switch (Both)_158d000xxxxxxx: off>: {'channel_1': 'click'}
dec 17 07:10:43 nuc.bachstraat20 docker[12783]: 2018-12-17 07:10:43 DEBUG (MainThread) [homeassistant.components.xiaomi_aqara] PUSH >> <Entity Wall Switch (Right)_158d000xxxxxxx: off>: {'channel_1': 'click'}
The 6th - 4th last lines appeared when I pressed the left button. The last 3 lines appeared when I pressed the right button.