I’m in the process of integrating my BBQ Thermometer into HA…and I would like to run HA, Mosquitto (MQTT broker) and if possible, RTL 433 (radio receiver/MQTT client) on the same RPi. Is it possible…and if so, could someone give me at least a clue where to start 
If you run either you run Home Assistant OS, or Home Assistant Supervised, the easiest way is to install the mosquitto add-on (official add-on store) and the RTL_433 add-on from https://github.com/accelle17/hassio-addons
Spent some time on this…and yes, you can run mosquito Node-red and HAAS on one RPi…and it’s likely that you can also run RTL-433, but I have to wait for the dongle to arrive.