DDP is probably the only good solution here for most EU customers, but frankly the hassle and expense of doing business in the EU is what keeps most US e-commerce companies from entering the market.
It is a shipping term, it stands for deluvered duty paid. Basically, customs duties are paid by the shipper and the item is delivered directly to the customer. From a logistics perspective it is a massive PITA, but for DTC sales in the EU it's the preferred option.
It stands for 'Delivery Duty Paid', i.e. customs charges, import tariffs, taxes, handling charges are included in the price and don't arrive as an unwelcome surprise.
I see a couple other folks jumped in. It’s basically a way to estimate duties and taxes up front so the EU customer knows the full price before they order.
The reality it that most EU customers already know the price before they order (or have a good idea it’s going to be 20% more). But they like to pretend they don’t.