Magento 2 Shipping Methods – Hide If Customer Not Logged In

• Try it with a shipping/billing address for which you have shipping defined above: DEU, ESP, GBR, GBR, IRL, NLD
• Try it with weight vs. destination. What's the result then?
• Can you provide us with a sample CSV?

Let's say that the attribute code is called attribute_code so the getter name is getAttributeCode().

You need to create an arround plugin on the flatrate carrier model and UPS carrier model where you can check your conditions and return or not the shipping rate result.

You need to create a module and add this in the di.xml file

<type name="Magento\OfflineShipping\Model\Carrier\Flatrate">
    <plugin name="[module]-flatrate" type="[Vendor]\[Module]\Plugin\Flatrate" />
</type>

<type name="Magento\Ups\Model\Carrier">
    <plugin name="[module]-ups" type="[Vendor]\[Module]\Plugin\Ups" />
</type>

Then create the file [Vendor]/[Module]/Plugin/Flatrate.php

<?php 

namespace [Vendor]\[Module]\Plugin;

class Flatrate
{
    public function arroundCollectRates(
        \Magento\OfflineShipping\Model\Carrier\Flatrate $subject,
        \Closure $proceed,
        Magento\Quote\Model\Quote\Address\RateRequest $request
    ) {
        $items = $request->getAllItems();
        foreach ($items as $item) {
            if ($item->getProduct()->getAttributeCode()) {
                 //if your attribute value is true don't show this method
                 return false;
            }
        }
        return $proceed();
    }
}

and this plugin class that handles UPS shipping method [Vendor]/[Module]/Plugin/Ups.php

<?php 

namespace [Vendor]\[Module]\Plugin;

class Ups
{
    public function arroundCollectRates(
        \Magento\OfflineShipping\Model\Carrier\Ups $subject,
        \Closure $proceed,
        Magento\Quote\Model\Quote\Address\RateRequest $request
    ) {
        $items = $request->getAllItems();
        foreach ($items as $item) {
            if ($item->getProduct()->getAttributeCode()) {
                 //if one attribute value is true show the method
                 return $proceed();
            }
        }
        //if all the products had the value false don't show UPS.
        return false;
    }
}

But keep in mind that I didn't test the code so watch out for typos.