Install the extension via composer:
composer require yireo/magento2-loki-checkout-mollie
Next, enable the module:
bin/magento module:enable Yireo_LokiCheckoutMollie Mollie_Payment
Make sure the module Mollie_HyvaCheckout is disabled!
Tip: When not all your payment methods show up, note that the payment method listing of Magento is filtered with the listing that Mollie is able to serve. This is done by fetching active methods via the API (Mollie\Payment\Model\MollieConfigProvider::getActiveMethods). And this leads into specific settings for specific methods. For instance, the Dutch *Ideal` method is only there if the Magento currency is set to Euro, not US dollar.
It is possible with the Loki Checkou**t to swap the steps, making the Payment step the first and the Shipping step the last. However, be warned that not all payment providers support this. Some payment providers operate purely on the JavaScript level and require the Place Order button to be submitting their client-side data. Unfortunately, this can only be done if the Place Order button and the Payment details are shown at the same time.