You don't have to be PCI compliant for stuff like bank transfers or other forms of payment. Credit cards aren't the default payment method everywhere.
Maybe it's pay on pickup, or just a simple mail with sepa wire transfer instructions.
Also, the PSP can still use JS but your site still doesn't need to have it. Services like Mollie and Stripe offer checkout environments they host, meaning you still don't have to use JS on your site.