When the final Place Order button is hit, the quote is converted into an order. If this takes a long time, this document hopefully gives you some hints on what might be wrong. The core logic of the LokiCheckout is actually quite straight-forward, so most likely, a specific setting in the environment or a third party extension is slowing things done.
When hitting the button for the final step, it might be that this takes forever. First of all, make sure there are no JavaScript errors in the Error Console - they could be preventing further JavaScript execution.
It might be that your system is not configured properly for sending email, because of which an attempt to send an email leads into a huge delay and potentially a PHP timeout. You might want to try to disable all SMTP communication (Advanced > System > Mail Sending Settings > Disable Email Communications) and/or enable asynchronous sending (Sales > Sales Emails > General Settings > Asynchronous sending).
Make sure to backup the original settings first.
magerun2 config:set system/smtp/disable 1
magerun2 config:set sales_email/general/async_sending 1
If the checkout finishes quickly and without errors, after changing these settings, you know that the slowness is due to email sending.
Third party shipping methods and payment methods might be slow, because they might be connecting to remote APIs. To see if this is to blame, temporarily enable a plain shipping method (like: flat rate or tablerates) and plain payment method (like bank transfer).
If the checkout finishes quickly and without errors, with these plain methods used, you know that the slowness is due to the third party extension.