There are other similar queries, some related Shopify community forum threads linked below, although I don't yet find an option on Shopify to add a fee based on a payment method.
Please also aware that depending on your store's region, the Payment Service Directive 2 (PSD2), in effect since 2018, introduces a surcharge ban for many European B2C transactions. Surcharging isn’t permitted for consumer payments made with most debit and credit cards. In addition, surcharging isn’t permitted when payments are made using standard credit transfer or SEPA Direct Debit. In the instances where surcharging is permitted, the amount of the surcharge can never be higher than the actual costs incurred by the merchant in accepting the payment method.
Additionally, if you have integrated Klarna Pay later (invoice) or Pay in 3, only fees that are considered 'insignificant' are allowed under law since these are considered so-called 'unregulated credit products'. In some markets, no fees at all are allowed. In order to protect our mutual customers and ensure compliance with applicable laws, Klarna does not allow merchants to add fees that are charged solely due to the customer choosing to pay with Klarna.