Apples and steamed cauliflower. Yum - gotta make this again soon.
Or broccoli – I suppose anything commonly eaten with a cheese sauce would be good for fondue.
As far as things to dip are concerned, everything I was going to suggest has been mentioned.
So I’ll just add: don’t forget to serve a fresh green salad, preferably with a nice tart rather than creamy dressing, or something like that to counter-balance the rich density of the fondue itself.
Sodium citrate is great for keeping the sauce emulsified.
A bit of sodium citrate solves the issue as well.
ETA: Ninja’d!
What is sodium citrate usually found in? Or is it common for it to be available in pure form in grocery stores?
“Sour salt”, or you can order it from Amazon or Modernist Pantry.