Probably not worth it, given that the EU caps the credit card fees at 0.3%, 0.2% for debit cards.

Well the cap is only on the interchange fee, there are several other fees to add to it... example: https://www.adyen.com/pricing

Processing a Mastercard card is "$0.13 + "Interchange+" + 0.60%" where the "Interchange+" would be 0.30% for EU. So more like €0.10 + 0.90% so for €10.00 product, it would be €1 of fee (1.00%). Much less than here in US, but still not negligible for small businesses that run on thin margins (and 20% VAT).