How to avoid subscribing to the Shopify Advanced Plan and still use shipping apps from third party developers.
No, you don't have to be on the Shopify Advanced Plan to use shipping apps from third part developers.
To use the Small Package Quotes or LTL Freight Quotes app in Shopify, your Shopify subscription must contain a feature called Third-party calculated shipping rates. This feature is standard on the Advanced Shopify plan. It can be added to the Basic Shopify or Shopify plan by calling Shopify customer support (888-746-7439).
Adding the feature to one of these other plans will increase your monthly subscription rate by $20. Shopify will add the feature to your existing Shopify plan for free if you agree to annual (instead of monthly) billing.