Installing Shelly app makes homey unresponsive

Nope, and Athom decided not the investigate the issue as it only affects a small number of people. For more info see https://github.com/jghaanstra/cloud.shelly/issues/28.

Feel free to further troubleshoot it and supply more details as to why this is happening.

Unfortunately, not. I ended up sending back my Shelly devices. I did however test another brand of WiFi devices and that did work just fine. (wasn’t happy with the noise level of the lightbulbs though)
So it’s Hue ($$$) for now.

That’s too bad. I look a little further. I am satisfied with Shelly

Looks like this issue is back again. After update 4.3.8 of the shelly app my Homey started rebooting again. After deleting the Shelly-app the Homey works fine.