Disable SSL when downloading package and libraries index file

[Pandede]

The Arduino IDE keeps showing Error downloading https://downloads.arduino.cc/libraries/library_index.json
I've encountered the same issue when I was downloading the package_index.json, then I figured it out that is the SSL problem (the enterprise firewall), thus I add http://downloads.arduino.cc/libraries/package_index.json into "Additional Board Manager URLs" and it worked fine.
I've modified com.sun.management.jmxremote.ssl=false in the file ./java/lib/management/management.properties, but it still doesn't work.
How can I disable the SSL?

Arduino Version: 1.8.19
OS: Ubuntu 18.04

[Pandede]

I just found the solution of the issue.
This error occurred due to the self-signed certificate, add certificate of my company to Java keystore is required.

The link of solution is here (Linux):
https://forum.arduino.cc/t/arduino-ide-cant-download-libraries-and-boards/650155/11