Just getting back to this and solution by Peter_n works! Awesome!
I am now running Mag2.4.4 and noticed the file is somewhat updated, but no matter: Simply add the 2 lines in below to the last function in the in the file noted by Peter_n (it's all the way at the end of the file).
->setCustomerFirstname($quote->getBillingAddress()->getFirstname())
->setCustomerLastname($quote->getBillingAddress()->getLastname())
It will look like this:
protected function prepareGuestQuote()
{
$quote = $this->_quote;
$billingAddress = $quote->getBillingAddress();
/* Check if Guest customer provided an email address on checkout page, and in case
it was provided, use it as priority, if not, use email address returned from PayPal.
(Guest customer can place order two ways: - from checkout page, where guest is asked to provide
an email address that later can be used for account creation; - from mini shopping cart, directly
proceeding to PayPal without providing an email address */
$email = $billingAddress->getOrigData('email') !== null
? $billingAddress->getOrigData('email') : $billingAddress->getEmail();
$quote->setCustomerId(null)
->setCustomerFirstname($quote->getBillingAddress()->getFirstname())
->setCustomerLastname($quote->getBillingAddress()->getLastname())
->setCustomerEmail($email)
->setCustomerIsGuest(true)
->setCustomerGroupId(\Magento\Customer\Model\Group::NOT_LOGGED_IN_ID);
return $this;
}
