There are a handful of different eligibility requirements that developers must meet to be able to distribute apps via their website:

• Be enrolled in the Apple Developer Program as an organization incorporated, domiciled, and or registered in the EU (or have a subsidiary legal entity incorporated, domiciled, and or registered in the EU that’s listed in App Store Connect). The location associated with your legal entity is listed in your Apple Developer account.
• Be a member of good standing in the Apple Developer Program for two continuous years or more, and have an app that had more than one million first annual installs on iOS in the EU in the prior calendar year.
• Agree to, among other things,
  • Only offer apps from your developer account.
  • Be responsive to communications from Apple regarding your apps distributed through Web Distribution, particularly regarding any fraudulent, malicious, or illegal behavior, or anything else that Apple believes impacts the safety, security, or privacy of users.
  • Publish transparent data collection policies and offer users control over how their data is collected and used.
  • Follow applicable laws of the jurisdictions where you operate (for example, the Digital Services Act, the General Data Protection Regulation, and consumer protection laws).
  • Be responsible for handling governmental and other requests to take down listings of apps.