This is Magento bug. Wrong paths to Windows are generated. The fixed fix is

Magento 2.3.0

/vendor/magento/framework/View/Element/Template/File/Validator.php:114

the string

$realPath = $this->fileDriver->getRealPath($path);

$realPath = $this->fileDriver->getRealPath($path);

to replace

$realPath = str_replace(‘\’, ‘/’, $this->fileDriver->getRealPath($path));

Magento 2.2.7

/vendor/magento/framework/View/Element/Template/File/Validator.php:113

code

protected function isPathInDirectories($path, $directories)
{
if (!is_array($directories)) {
$directories = (array)$directories;
}
foreach ($directories as $directory) {
if (0 === strpos($this->fileDriver->getRealPath($path), $directory)) {
return true;
}
}
return false;
}

to replace

protected function isPathInDirectories($path, $directories)
{
$realPath = str_replace(‘\’, ‘/’, $this->fileDriver->getRealPath($path));
if (!is_array($directories)) {
$directories = (array)$directories;
}
foreach ($directories as $directory) {
if (0 === strpos($realPath, $directory)) {
return true;
}
}
return false;
}