I installed a Rachio 2 in Spain (Huelva) a couple of years ago and overcame the power adaptor issue by buying a UK adaptor and then making a short extension lead with european plug on one end and a UK 3 pin trailing socket at the other end which with power supply plugged in still fits into the Rachio external enclosure.
Whilst it generally works well, I find the setup and Rachio instructions very frustrating e.g. the Rachio website says Seasonal Shift works by “referencing 30 years of historical weather Almanac data in your area” but if the truth be known, it only works in USA and Canada, so completely useless in Europe. You have to enter your location into Rachio so why can’t the software simply disable the functionality that they know full well will not work? And it would save me getting monthly emails telling me that Seasonal Shift has adjusted the watering - by 0 minutes!
And beware that if you ask Support for assistance you will probably be told “I wanted to let you know that our products are unfortunately not intended for distribution outside of the United States and Canada” which I find frustrating as the Sales Team advise you to buy from Amazon.com and there are plenty of posts from Rachio staff on the Rachio Community encouraging an international community too! Anything for a quick buck, I suppose…