ha-api.mcc.miui.com is a subdomain of miui.com, which belongs to Xiaomi, a major electronics manufacturer. The page you see is a default server welcome screen for a tool called 'mife' — this is not a consumer website or a storefront. It's an internal API endpoint, likely used by Xiaomi's own systems or developers.
For a site of this type, the lack of contact info, privacy policy, or social media links is completely normal. You wouldn't walk up to a server room and ask for a customer service number. The SSL certificate is valid and hosted on Microsoft Azure, which adds to the credibility.
If you're a developer integrating with Xiaomi services, this endpoint is legitimate. If you're a regular user, you probably won't ever interact with this site directly. There's no evidence of scams, and the domain's parent company is well-known. So, yes, ha-api.mcc.miui.com is safe — it's just not a site designed for the general public.