"Que" as in "only" in fragments

Question

For whatever reason, I increasingly use ne ... que to express "only", as opposed to perhaps juste or seulement.

But there are some contexts where I'm not sure if it's possible or stylistically desirable, and if so, how to do it. One of those contexts is in fragments. For example:

— Tu regardes des films d'horreur ?
— Only rarely.

Each of these sounds like an unlikely or strictly ungrammatical rendering of "only rarely":

✗ Juste rarement.

✗ Seulement rarement.

✗ Rien que rarement.

I note that rien que is flexible in the sense that you can use it in some contexts without any verb to negate, but here it doesn't seem to suit.

Are my premises right? What's the solution? Must one paraphase?

Answer 1

For whatever reason, I increasingly use ne ... que to express "only", as opposed to perhaps juste or seulement.

Well you're in luck, this is usually the idiomatic way of saying it.

The three translations you suggest are not idiomatic (at least in France). I don't think they're "strictly ungrammatical", but you shouldn't use them – a native speaker wouldn't say that.

Instead I would answer simply :

Tu regardes des films d'horreur ?
Rarement.

As it is implied that it is "only" rarely. Or if you prefer:

Oui, mais rarement.

The "mais" indicating that you're nuancing your answer, the same way that "only" does.