MeR being the meta-distro or "trunk", can be the central site/forum (xxxx.merproject.org) that links to all MeR-derived sites/infra/fori:

talk.sailfishos.org
talk.nemomobile.org
talk.plasma-active.org
etc.

Or if that's too cumbersome we could have:

sailfish.merproject.org
nemo.merproject.org
plasma.merproject.org

Or something like that...