Strange behavior when installing uber-juno extension

I just installed Atom on Ubuntu 18.04 using atom-amd64.deb, launched it and selected uber-juno extension for installation. I’m facing a grayed-out window with a text input dialog and menu bar active. Was the installation successful? What should I enter into the text box?

It seems to be a problem with Juno. After clicking around the main menu, which was functional except of Juno sub-menu, I clicked Juno->Release Note and uber-juno installation got unstuck. I will report this issue on github.