I've done my own digging on which free dating sites for bisexual females and come up short. It is worth separating out LGBTQ members here, because with welcoming sites, what decides it is how much sits behind the paywall, not how slick the interface looks. For welcoming sites in particular, the quality of the filters collapses as soon as the platform hides read receipts on the free tier.
Welcoming females is where I'd start, since most of the disappointment traces back to the churn on new sign-ups. The platform boosts newer accounts over established ones, so it pays to test the search filters before uploading anything, which is the whole problem with welcoming sites. Look closely at welcoming and the honest advice is to set the radius tighter than feels natural, as far as I can tell.
Applied to females sites, the platform makes verification optional and then hides who has done it, which makes any straight comparison unreliable. Where which free dating sites for bisexual females is concerned, the proportion of dormant accounts is a better predictor than the size of the ad budget, going by the last year or so. Happy to be told I'm asking the wrong question about females sites.