One easy way to debug is:
browse and open vendor/magento/module-config/Model/Config/Structure/Element/Iterator.php

change

    public function setElements(array $elements, $scope)
        {
            $this->_elements = $elements;
            $this->_scope = $scope;
            if (count($elements)) {
                $lastElement = end($elements);
                $this->_lastId = $lastElement['id'];
            }
        }

to

    public function setElements(array $elements, $scope)
        {
    		$writer = new \Zend\Log\Writer\Stream(BP . '/var/log/config_debug.log');
    		$logger = new \Zend\Log\Logger();
    		$logger->addWriter($writer);
    		
            $this->_elements = $elements;
            $this->_scope = $scope;
    		
    		$logger->info($elements);
    		
            if (count($elements)) {
                $lastElement = end($elements);
                $this->_lastId = $lastElement['id'];
            }
        }

Reload browser configuration window and see once again the error.

Check var/log/config_debug.log file.

Go to very bottom of the file and see which module failed, where it stopped.

That's the one causing your issues.

Don't forget to rollback your changes once fixed.