1. I have installed JD Berlin Quickstart on my webserver today and it has two error messages on home and packages links.
See the attached file below (I wrote here about this error message somedays ago before I purchased the JD Berlin Template and said it was solved?)
How can it be solved?
2. Is there a problem if I upgrade to Joomla 3.9.26 after already having the JD Berlin template installed?
1. The errors really appear where a user with ID (in your case 324) has been deleted, which is the author of the particular article/page. If you edit the page/article and change the author to yourself. The error should go away.
2. You can upgrade and that shouldn't be an issue.
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