I cannot for the life of me find any links to share activities, or to get embed html code to put my activites in a blog post. Using Garmin Connect "modern".
Navigate to your activity, and make sure that privacy is set to "Everyone". Then the sharing symbol (the two lines with three dots, just next to the padlock symbol) will be enabled and there you can select how to share your activity. By choosing "More.." you get a host of different options, and by choosing Embed you get the html-code to insert on your web page of choice.
