You can determine it from the online SSL Certificate checker site. For example, sslshopper.com.
The process to determine if the certificate chain is completed or not?
Step 1: First, you need to open an online SSL Certificate checker site like sslshopper.com.
Step 2: Select the option SSL Checker and click on it.
Step 3: Enter the hostname/website name in the Server Hostname field and click the Check SSL button.
Step 4: Once you click on the button, you will get the result below. If the certificate chain is not completed, you will get a warning sign in the Chain certificate section. You will get a good sign in the Chain certificate section if it is complete.