Currently ostree-list is hosted at mail.gnome.org. Per the mailing list move initiative I’ve asked the ostree maintainers in a public bug if they’d like to move to Discourse. See https://github.com/ostreedev/ostree/issues/2216 for the public bug and the resulting discussion.
Ostree is a bit unlike most existing GNOME mailing lists in that ostree isn’t as “GNOMEy” as most of the other mailing lists. It should be considered more “World” or “related but GNOME”. It wouldn’t be good to give the impression it only works for GNOME, or have a discussion mingled with loads of GNOME specific things (I think).
Could the site maintainers together with ostree figure out a good place? I’ll reference this topic/thread in the ostree bug. Thanks!!
PS: Aside from ostree there’s also NetworkManager and Midnight Commander (user+dev lists) in a similar situation