Yea already look around and I found you there as well 
But I think I found where it is going wrong, it is the /+/+ in the Topic path.
Bellow the explanation and I hope some one can fix this as it took me 8 hours to figure this out…
I got a lilygo_rtl_443_ESP.
Discovery is working as I can find my temp sensor however as soon as I add it it is going to a “UNKNOWN” state. (Using Openhab3).
The lilygo itself is working but if I look at the configuration (MQTT Explorer)
“stat_t”:"MQTT01/OpenMQTTGateway_lilygo_rtl_433_ESP/SYStoMQTT
{"stat_t":"MQTT01/OpenMQTTGateway_lilygo_rtl_433_ESP/SYStoMQTT","avty_t":"MQTT01/OpenMQTTGateway_lilygo_rtl_433_ESP/LWT","name":"SYS: Auto discovery","uniq_id":"0C8B95A5CC54-discovery","retain":true,"val_tpl":"{{ value_json.discovery }}","pl_on":"{\"discovery\":true}","pl_off":"{\"discovery\":false}","pl_avail":"online","pl_not_avail":"offline","stat_on":true,"stat_off":false,"cmd_t":"MQTT01/OpenMQTTGateway_lilygo_rtl_433_ESP/commands/MQTTtoSYS/config","device":{"identifiers":["0C8B95A5CC54"],"name":"OpenMQTTGateway_lilygo_rtl_433_ESP","model":"[\"LilyGo_SSD1306\",\"rtl_433\"]","manufacturer":"OMG_community","sw_version":"v1.5.1"}}
Temp sensor:
stat_t":"+/+/RTL_433toMQTT/Nexus-TH/2/1
{"stat_t":"+/+/RTL_433toMQTT/Nexus-TH/2/1","dev_cla":"temperature","unit_of_meas":"°C","name":"temperature","uniq_id":"Nexus-TH-2-1-temperature_C","val_tpl":"{{ value_json.temperature_C | is_defined }}","state_class":"measurement","device":{"identifiers":["Nexus-TH-2-1"],"connections":[["mac","Nexus-TH-2-1"]],"model":"Nexus-TH","name":"Nexus-TH-2-1","via_device":"OpenMQTTGateway_lilygo_rtl_433_ESP"}}
Code that is working for me: (Just add a generic node and configure the channels.)
UID: mqtt:topic:88dabb9100
label: MQ_443_Garden01
thingTypeUID: mqtt:topic
configuration: {}
bridgeUID: mqtt:broker:b6a54d9f0e
location: Garden
channels:
- id: Battery
channelTypeUID: mqtt:number
label: Battery
description: null
configuration:
stateTopic: MQTT01/OpenMQTTGateway_lilygo_rtl_433_ESP/RTL_433toMQTT/Nexus-TH/2/1
transformationPattern: JSONPATH:$.battery_ok
- id: Temperature
channelTypeUID: mqtt:number
label: Temperature
description: null
configuration:
stateTopic: MQTT01/OpenMQTTGateway_lilygo_rtl_433_ESP/RTL_433toMQTT/Nexus-TH/2/1
transformationPattern: JSONPATH:$.temperature_C
- id: Humidity
channelTypeUID: mqtt:number
label: Humidity
description: null
configuration:
stateTopic: MQTT01/OpenMQTTGateway_lilygo_rtl_433_ESP/RTL_433toMQTT/Nexus-TH/2/1
transformationPattern: JSONPATH:$.humidity
Just let me know if you need more information!