If the Plugin you wish to report a bug for is part of the default Matomo (Piwik) distribution, then you can simply report the bug like you would report for Matomo platform. Learn more.
If you wish to report a bug for a plugin that is published on the Marketplace, open this plugin’s page to look for Support information. For example on the LiveTab plugin page on the Marketplace, click on
Support tab, and you will find that the developer indicates that issues should be reported in github.com/tsteur/piwik-livetab-plugin/issues.
If the Plugin you wish to report a bug for does not have information on how to ask for Support, we recommend to create an issue in the Github issue tracker for this plugin. To find the Github issues tracker, open the Plugin page on the Matomo Marketplace, click on the « Github » link, and then click on « Issues ».
See also: How do I create a good bug report?