any decent 12Vdc power supplies that can be used as a 12V trigger?

From my understanding, The Micromega M-100 has a 12V trigger input, I need a 12V source to trigger it. I was going to plug a 12V power supply into a smart plug and control it with Alexa ( So I'd have a sleep timer )

Your amp will work, even without anything connected to trigger input.  Yes, amp turns ON with the presence of +12V, but this voltage is already there (pulled-up internally to 12V).  Try shorting this input to GND - it will turn your amp OFF while removing short will turn it back ON.  All you need is switch.

 

I just discovered my WiiM pro has a 12V trigger, going to try a cable from WiiM to amp.

I also discovered by e-mailing Micromega, Thier triggers are labeled backward due to a manufacturing issue, so I was plugged in to the output instead of the input. Waiting on my 2.5mm to 3.5mm trigger cable to come in tomorrow so I can try it with the WiiM Pro.

Got the cord for the WiiM pro from Amazon and it works great. I believe a switched mode 12V power supply would work with the smart plug too, the power supply I got probably would work but it takes a while to discharge so the voltage drops enough to shut the amp off. I never left it on long enough to find out.