Stripe

Recently Stripe payment processor announced that Swish payments for the Swedish market are now supported – https://docs.stripe.com/payments/swish.
The manual configuration seems pretty straightforward – https://docs.stripe.com/payments/swish/accept-a-payment?web-or-mobile=web&payments-ui-type=stripe-hosted#enable-swish-as-a-payment-method.

So, I assume it is not that hard to add support to the WooCommerce plugin for Stripe payment, to support Swish as an option.

Another request for this exists – https://wordpress.org/support/topic/support-for-swish/.