Where would you find 20 long-term couples to test a private date-night memory app?

I’ve built a very simple web app for couples who already intentionally schedule date nights.

It’s not a date idea generator.
It’s just a simple and private shared timeline where couples log their date nights so they don’t blur together over the years.

I’m trying to validate one thing:
If 30–40% of couples add 2+ entries and return after 2 weeks, there’s signal.

I need 15–25 real couples (not friends) to use it for 30 days.

Constraints:
– No paid ads
– No leveraging personal network
– Organic only
– Target: long-term couples (3+ years) who already try to prioritise date nights

If you were solving this distribution problem, where would you go online?

I’m especially interested in niche communities rather than broad platforms.