Hi, thanks for the feedback Sergey! I actually didn't realize this.
The Blender docs say that Add-ons are saved with App Templates, but also says you can define a custom path for "template-specific" add-ons, which I haven't done up to this point, but I think it's what I'll have to do from now on to avoid issues like the one you're having!
Until then, I've updated the main page with links to all the add-ons (either gumroad or github), and the link for my own Unreal Objects add-on is at the bottom of the page.
Thanks again for bringing this to my attention, I will fix this up in the next update, until then you can download from the links on the main page and install manually. Sorry for the inconvenience, and thanks for trying the template!