I am getting the following:
Unable to download updates from "extensions.gnome.org": [*/*/*/source/shell-extensions/*] failed to download https:// extensions.gnome.org//static/extensions.json: Cannot resolve hostname
I am running the out of the box Ubuntu Software v3.28.1, which I agree is a nice way to manage the software on my system.
I was able to install and launch PyCharm Pro with no issues, though I may try the snap later. I was also able to install and launch Atom, VLC, Zoom, Chromium, Google Chrome and VirtualBox without issues, so when time permits I'm guessing I need to go upstream into source code, as I'd like to understand where the error message came from and if it means anything.
The message did not reappear when I restarted the machine.
I haven't yet tried to figure out steps to reproduce.