I have a similar problem with IDE V2.3.3 on Windows. The message is:
Downloading index: package_index.tar.bz2
This message appears every time I start the IDE and the progress bar beneath it reaches about half-way and stops. I do not have any of the ESP32 boards installed, so I cannot follow the advice above to un-install them.
When I try to compile a sketch, I get:
Compiling sketch...
and that process hangs too. The 'cancel' button is effective, and I get 'User abort' in the Output pane.
Any ideas?