I'm running Emacs 26.3 on Linux Mint 20. I am using paradox, but this also happens when I use the vanilla Emacs packages interface.
When I call
list-packages, the Paradox Menu section of the mode line just says "Loading', and the little progress indicator keeps going, but it never completes. I have a bunch of different package archives enabled, but I commented them all out and re-enabled them one by one, and it's only melpa that causes the problem. Even melpa-stable works.
Anybody encountered this? Any troubleshooting steps to try?