I recently did a distro update a few days ago, which fixed an issue I had with my “Super” key not opening the application menu but then Discover would not launch, but Updates via the CLI worked fine.
I did the following recommendations in this post:
I tried the strace plasma-discover command but it was still hanging at some point - no joy.
I ran the pkcon update which did actually do updates.
I then ran the sudo apt purge plasma-discover-backend-snap. I did attempt to run Discover to see if it would work, which it did not. However, after rebooting the computer, Discover is now working again as expected. It did ask for the admim PW in order to update repositories.
Thanks!