Got it, Gen4 has Zigbee too in addition to Matter, I guess it’s worth it as first Shelly device to have more options.
MQTT if I understand correctly requires not only the SmartThings hub and this custom driver but another machine running 24/7 to run the MQTT broker.
I’m surprised with your experience with Matter lights, I have 9 WiZ and 3 Nanoleafs and don’t really remember if they’ve been offline in a year using the Aeotec hub. My Matter sensors have been stable too, except the Aqara P2 door sensor which goes offline for a couple minutes from time to time but that’s running a two years old firmware because Aqara.