Direct MQTT broker connection without bridge (mosquitto)

Could be very intresting to get bidirectional connection from ST to a MQTT broker without the use of an intermediary bridge.
ST. JOHN JOHNSON did a fantastic work (MQTT Bridge [device + app]) but it needs some hw/sw/complexity/costs between our ST and the MQTT broker.
It is possibile (or maybe impossibile for technological problems ?) to develop an app/dh that read/post data to an MQTT broker? Nowdays there are MQTT brokers like mosquitto ( running in cloud or locally, for example in synology nas or similar it’s very easy to do that also for a newbie like me.
I’ve found nothing here in community.
Thank you for help.