<script type="text/x-magento-init">
    {
        "[data-block='free-shipping-bar']": {
            "Magento_Ui/js/core/app": <?php /* @escapeNotVerified */ echo $block->getJsLayout() ?>
        },
        "*": {
            "Magento_Ui/js/block-loader": "<?= /* @escapeNotVerified */ $block->getViewFileUrl('images/loader-1.gif') ?>"
        }
    }
</script>

class AddFreeShippingBarVariables
{
    public function afterGetJsLayout(\Magento\Checkout\Block\Cart\Sidebar $subject, $jsLayout)
    {
        $jsLayout = json_decode($jsLayout, true);

        $freeShippingBarConfig = $this->arrayManager->get(self::FREE_SHIPPING_BAR_CONFIG_PATH, $jsLayout);

        if (!empty($freeShippingBarConfig)) {
            $freeShippingBarConfig['freeShippingFrom'] = $this->shippingMethodsHelper->getMinimumFreeShippingAmount();
            $freeShippingBarConfig['priceFormat'] = $this->taxHelper->getPriceFormat($this->storeManager->getStore()->getId());

            $jsLayout = $this->arrayManager->set(self::FREE_SHIPPING_BAR_CONFIG_PATH, $jsLayout, $freeShippingBarConfig);
        }

        return json_encode($jsLayout);
    }
}

class AddFreeShippingBarVariables
{
    public function afterGetJsLayout(\Magento\Checkout\Block\Cart\Totals $subject, $jsLayout)
    {
        $jsLayout = json_decode($jsLayout, true);

        $freeShippingBarConfig = $this->arrayManager->get(self::FREE_SHIPPING_BAR_CONFIG_PATH, $jsLayout);

        if (!empty($freeShippingBarConfig)) {
            $freeShippingBarConfig['freeShippingFrom'] = $this->shippingMethodsHelper->getMinimumFreeShippingAmount();
            $freeShippingBarConfig['priceFormat'] = $this->taxHelper->getPriceFormat($this->storeManager->getStore()->getId());

            $jsLayout = $this->arrayManager->set(self::FREE_SHIPPING_BAR_CONFIG_PATH, $jsLayout, $freeShippingBarConfig);
        }

        return json_encode($jsLayout);
    }
}

class ShippingMethods extends \Magento\Framework\App\Helper\AbstractHelper
{
    public function getMinimumFreeShippingAmount()
    {
        $minimumAmount = null;

        foreach ($this->freeShippingMethodsProvider->getShippingMethodsWithFreeShipping() as $methodData) {
            if (!$minimumAmount || (int) $methodData['value'] < $minimumAmount) {
                $minimumAmount = (int) $methodData['value'];
            }
        }

        return $minimumAmount;
    }
}

class FreeShippingMethodsProvider
{
    public function getShippingMethodsWithFreeShipping()
    {
        $activeCarriers = $this->shippingConfig->getActiveCarriers();
        $methods = [];

        foreach ($activeCarriers as $code => $model) {
            .....

            $freeShippingSubtotal = $this->configuration->getFreeShippingSubtotal($code, $subtotalField);
            $freeShippingTitle = $this->configuration->getFreeShippingTitle($code);

            $methods[$code] = [
                'title' => $freeShippingTitle,
                'value' => $freeShippingSubtotal
            ];
        }

        return $methods;
    }
}