Does anyone know if there is an English version of the SJ.No website?
That's weird; I don't see a way to switch to English, either. Maybe if you try the chat function (round blobs near the lower right on my PC screen) you can get a link.
Doesn't look like it. Though Google Translate will translate the site into English in your browser.
Alternatively, the man in seat 61 recommends https://www.vy.no/en or https://entur.no/ if you want to buy tickets etc.
I've never tried to change the language of their site before, but I had a look and I couldn't find a way.
Use entur.no instead.