Someone already mentioned the NHS website, but also the Mayo Clinic's is great [2]. We have a great one run by the Swedish state too [3]. I think the article is wrong that "we accept" them though, they've just SEO spammed themselves over anything that actually is useful. It's not like we vote on search results (yet.) NHS, Mayo Clinic or others that must exist would be top if these assholes didn't scam their way in.
1. https://www.nhs.uk/conditions/
2. https://www.mayoclinic.org/diseases-conditions
3. https://www.1177.se