Faceting after distinct except for specific attribute?

I’m trying to allow users to refine a set of results by a timestamp attribute. The results are distinct by an ID, but each result could have a few different duplicates where the timestamp will be different:

e.g. We have a number of trips, each of which has a number of departure dates.

[{
tripId: 123,
departureDate: 123456, // a timestamp
country: UK
},
{
tripId: 123,
departureDate: 23456,
country: UK
}...]

I want to only show one result per trip ID, so have set up distinct by that attribute. I also only want my facet count for the country attribute to show distinct counts (e.g. UK (1)).

However, I’d like to allow users to choose a departure date range. But if we use a regular connectRange component and faceting to power it, I don’t currently get the full range choices since it will only give me a single value per tripId.

I could create a range slider that doesn’t work on faceting, but before I do, is there any way to un-distinct my departureDate attribute?

Thanks