It’s fairly low-volume here - I tend to post GB-specific questions of my own to the talk-GB mailing list, but do answer questions here (often from people for whom the forum is the default for their community, so they not unnaturally assume that other communities are the same).
I had always assumed that the reason why the OSM UK chapter (which is a subset of people involved in OSM in the UK) wanted a separate forum was that they wanted a closed rather than an open space, together with the ability to do e.g. polls which aren’t natively supported by FluxBB (though it looks like there’s an add-on for that: https://fluxbb.org/resources/mods/simple-poll/ ), and at least one of the people involved in setting up the UK chapter was not a fan of open mailing lists.
At OSM France we decided to continue using Loomio (with the reduced rate), because it allows to officially validate the decisions. We don’t have any other tools as practical as this one yet.
We are waiting to see what will happen.