I worked with @chapoi to merge this into core this week, and it’s here now:
You should uninstall this theme component if you have it installed.
A new post_menu button, copyLink, is added and used as the default instead of share. If site owners want the old behaviour back, they just need to change the post_menu site setting to use the share button instead of copyLink.
On desktop, this button will copy the link of the post to the user’s clipboard and show a nice animation. On mobile the native share menu will be shown.