Hi,
There is a very easy way to send Codes via MQTT through the Sonoff RF Bridge which does not need to bind codes to rfkeys.
Open the Tasmota Console runiing on your RF Bridge. Then press the “ON” Button on your original remote. In the console you’ll see something like :
{"RfReceived":{"Sync":8970,"Low":300,"High":870,"Data":"0414025","RfKey":"None"}}
Data":“0414025” contains the code in hex. form.
Simply publish this code as payload #0414025 (# is very important) to the topic cmnd/RF_Bridge/rfcode
You can repeat this with many codes as you like.
In configuration.yaml file, I defined the switch like this:
- platform: mqtt
name: "RFPlug-1"
command_topic: cmnd/RF_Bridge/rfcode
availability_topic: "tele/RF_Bridge/LWT"
payload_available: "Online"
payload_not_available: "Offline"
payload_on: "#0414025"
payload_off: "#0414026"
optimistic: true
In Home Assistant, the Switch will appear like this:

Hope this helps you in your setup.