Another year, same ol' stuff.
None of my credit cards with no forex fees work on SJ's website or the app.
An older thread on Trip Advisor suggested using
https://www.snalltaget.se/en but that also didn't work. I could try via PayPal, but I would need to add a credit card.
Chatting with SJ, they recommended
https://www.omio.com (which I guess used to be goeuro.com?), which actually worked, but it is about a 7% mark-up compared to SJ's website/app. While I'll accept that for a one-off trip, I need to buy 23-27 more tickets across five trips!