I got this Warning in my Dashboard and I reported as asked for:
WARNING: /plugins/CoreVisualizations/JqplotDataGenerator/Evolution.php(89): Deprecated - Creation of dynamic property Piwik\Plugins\CoreVisualizations\JqplotDataGenerator\Chart::$dataTable is deprecated - Matomo 4.13.3 - Please report this message in the Matomo forums: https://forum.matomo.org (please do a search first as it might have been reported already) (Module: VisitsSummary, Action: getEvolutionGraph, In CLI mode: false)
WARNING: /plugins/CoreVisualizations/JqplotDataGenerator/Evolution.php(89): Deprecated - Creation of dynamic property Piwik\Plugins\CoreVisualizations\JqplotDataGenerator\Chart::$dataTable is deprecated - Matomo 4.13.3 - Please report this message in the Matomo forums: https://forum.matomo.org (please do a search first as it might have been reported already) (Module: VisitsSummary, Action: getEvolutionGraph, In CLI mode: false)
I also got this Warning in my Dashboard and I reported as asked for:
WARNING: /plugins/CoreVisualizations/JqplotDataGenerator/Evolution.php(89): Deprecated - Creation of dynamic property Piwik\Plugins\CoreVisualizations\JqplotDataGenerator\Chart::$dataTable is deprecated - Matomo 4.13.3 - Please report this message in the Matomo forums: https://forum.matomo.org (please do a search first as it might have been reported already) (Module: VisitsSummary, Action: getEvolutionGraph, In CLI mode: false)
found this thread when I was about to post a very similar error message after upgrading to Matomo 4.14.1 and having PHP set to version 8.2.4:
WARNING: /plugins/PagePerformance/JqplotDataGenerator/StackedBarEvolution.php(64): Deprecated - Creation of dynamic property Piwik\Plugins\PagePerformance\JqplotDataGenerator\Chart::$dataTable is deprecated - Matomo 4.14.1 - Please report this message in the Matomo forums: https://forum.matomo.org (please do a search first as it might have been reported already) (Module: PagePerformance, Action: getEvolutionGraph, In CLI mode: false)
It appears three times in a row when accessing the Administration page. The only difference between this and the original message from this post I could spot is the number after Evolution.php (89 vs 64) and the module (PagePerformance).
Reloading the pages removes the messages again.
Not sure but it seems to me there is still something going on in version 4.14.1.