Hi Taco,

1. What is "Helix Ultimate 6" ??? we don't such a version of template yet. We have 2.2.9.
2. Joomla has Debug/Max error mode that allows you to find file that cause problems.

Since the front-end message doesn't reveal which file is failing, turn on PHP stack tracing to locate the file causing the error:

1. Log into your Joomla Administrator panel.
2. Go to System > Global Configuration.
3. Open the Server tab and set Error Reporting to Maximum.
4. Open the System tab and set Debug System to Yes.
5. Save the settings and reload the page where the error occurred.

Probably, I am guessing, you are trying to use Search component that was removed in Joomla 6. You can use only SmartSearch (Finder). The legacy com_search component was deprecated and removed in favor of com_finder (Smart Search). If a menu item or module is still configured to use the legacy com_search engine, re-create the menu item or module using Smart Search view instead.

I am installing helixultimate_quickstart_j6_v2.2.9, and once the installation is complete and I try to access the site or the backend, I immediately get that error message.

Ok, but why you need demo with Helix, I don't get it, as I remember you are not beginner.

Enable debug mode using configuration.php file. If you want to spend some time. yes, I will talk with our dev team.

Otherwise , just install Joomla 6 + SPPB Pro and Helix template and start adding REAL content just after!