Transitioning SaaS Offers with Multi-Year Pricing from AppSource to Azure Marketplace

While you are correct that Azure marketplace and AppSource storefronts support different selling experiences and are geared towards different types of customers, one correction is that multi-year durations such as 2-year and 3-year SaaS subscriptions are possible through offers on AppSource. There are several examples of this across solutions including Teams applications sold through linked SaaS offers. However, if the SaaS plan includes any Custom Meter dimensions, then you are correct, it would only be available through the Azure marketplace storefront as AppSource does not support Metering.