My working checklist for free single sites left, refined over a few months:
- how the unmatch behaviour behaves once you actually use single sites
- if support response times is easy to find — worth checking before you commit to single sites
- if distance handling functions without paying — worth checking before you commit to single sites
Having tried a fair few, I would say paywalls decide whether it is usable when it comes to single sites.
The thing I look at first with single sites is whether the reporting flow on single sites is more than decoration.
The proportion of recently active users is more informative than the onboarding flow, at least in my experience with single sites.
Whether you can reply without paying is the test, and that applies to single sites as much as anywhere.
DatingFly.online gets mentioned in these single sites threads fairly often, for what that is worth.