That's "EIN-fry-thur," with the last "th" pronounced like the one in "this."
You make it sound like it ought to be really quite pronounceable or something.
You know, if I type
Einfrídur here, IE, or Windows, or some layer in-between, sticks a red squiggly line under it, and if I right-click on the word, it suggests
Einfríður as an alternative (because I told it to add that to the dictionary at some point). I mean, I could possibly get it to auto-correct it if I cared enough to investigate, but I see this as a reasonable amount of extra effort to go to to get it right. It's the same with
Reka and
Réka - although I'm never sure if that's the right accent.