From the screenshot, the extension is trying to require a file which is not available in Joomla 6:

• If you are not using latest version of the extension, update to latest version might solve the problem
• If you are using latest version and still get this error, that means the extension is not compatible with Joomla 6. You should report the issue to the developer of the extension and ask him to fix it

I'm closing this issue because it is not an issue with Joomla core.

thanks for your feedback.

The screen shot is talking about com_finder if you look correctly

when I disable com_finder component, the error is not displayed anymore.

so this is not a 3rd party error I think :-/

could you please re-open this issue?

To explain the reply from @joomdonation a bit more. You have an extension on your site that is trying to access a file within com_finder that is not present in Joomla 6.

It is not an error of com_finder but the error comes from something (a third party extension, I would say) is trying to require a file from com_finder. That file is available in Joomla 5 and earlier but was removed in Joomla 6 and it causes the error

You can go to System -> Global Configuration, set Debug System to Yes, then try perform the action which causes the error again, there should be stack trace displayed to show you where the error comes from

@brianteeman thank you for clarification ;-)

But as I said on my first post, I get also the error when I save a default joomla menu item....

That could still be a problem in a 3rd party extension - probably a finder plugin for that extension

I have enabled system debug.
When I save an article I get the error.

see here => https://prnt.sc/9ETu7FMgx-6y

As you can see from the screenshot, the error comes from finder/business plugin.

ok thanks for your feedback ;)