SiteGround uses Let’s Encrypt as a selling point on their website and even posts about making Let’s Encrypt available, but they do not mention that they do not support punycode domains/IDNs. You have to spend weeks talking to their technical support in order to learn this truth and by the time you’ve learned about this, you’ve already paid them for hosting services (sometimes, a year upfront, as that’s the only way to get their best rate).
Please update their listing to reflect that they do not support punycode domains so that they can’t rope in new customers.
I don’t see this as particularly malicious, but I agree that it may be useful for prospective customers to know, so I added a note on the forum thread. Hopefully they’ll improve their software and we can delete that note in the future.