I have a similar setup to @mark_cockcroft. My setup uses a dry contact relay (GoControl FS20Z-1) and a cheap monoprice tilt sensor.
This is a great video https://www.youtube.com/watch?v=vADl3FO0hGk (not mine but my inspiration). It does require soldering the dry contacts of the relay to an extra remote (didn’t want to mess up the wall button). The method in combination with a virtual momentary switch device handler; turning on mimics a momentary button press of the remote.
I also use the New smart app to link the virtual/simulated garage door device with two actual devices to combine the relay and the tilt sensor into one convenient tile in ST.
Since you have two doors, it would require you to have two separate setups. I don’t use alexa but I can confirm that Google Assistant will open with one caveat. It does not know that it is a door so I have to say “turn on the garage door opener”.