Recently I've encountered several occasions in which a FOSS project would have been interested in some reliable, independent mailing list hosting for their project communication.
I was surprised how difficult it was to find anyone running such a service.
From the user / FOSS project point of view, the criteria that I would have are:
operated by some respected entity that is unlikely to turn hostile, discontinue the service or go out of business altogether
free of any type of advertisements (we all know how annoying those are)
cares about privacy, i.e. doesn't sell the subscriber lists or non-public archives
use FOSS to run the service itself, such as GNU mailman, listserv, ezmlm, ...
an easy path to migrate away to another service (or self-hosting) as they grow or their requirements change. A simple mail forward to that new address for the related addresses is typically sufficient for that
If you think mailing lists serve no purpose these days anyways, and everyone is on github: Please have a look at the many thousands of FOSS project mailing lists out there still in use. Not everyone wants to introduce a dependency to the whim of a proprietary software-as-a-service provider.
I never had this problem as I always hosted my own mailman instance on lists.gnumonks.org anyway, and all the entities that I've been involved in (whether non-profit or businesses) had their own mailing list hosts. From franken.de in the 1990ies to netfilter.org, openmoko.org and now osmocom.org, we all pride oursevles in self-hosting.
But then there are plenty of smaller projects that neither have the skills nor the funding available. So they go to yahoo groups or some other service that will then hold them hostage without a way to switch their list archives from private to public, without downloadable archives or forwarding in the case they want to move away :(
Of course the larger FOSS projects also have their own list servers, starting from vger.kernel.org to Linux distributions like Debian GNU/Linux. But what if your FOSS project is not specifically Linux related?
The sort-of obvious candidates that I found all don't really fit:
https://lists.gnu.org/ is for official GNU projects
https://vger.kernel.org/ is specifically for Linux kernel development
https://lists.freedesktop.org/ is specifically for desktop/UI related projects
https://mail.kde.org/mailman/listinfo/ is hosting lists for KDE related projects
https://mail.gnome.org/mailman/listinfo/ likewise for Gnome projects
http://lists.fsfe.org/ appears to be for FSFE specific/internal lists only, and not a public service
http://lists.spi-inc.org/ likewise is for SPI's own lists only
https://opensource.org/lists also only runs lists for themselves
http://lists.digitalfreedomfoundation.org/lists/listinfo has no public lists
http://lists.jpberlin.de/ hosts tons of mailing lists for any kind of topic, but is a paid service
https://wiki.list.org/COM/Mailman%20hosting%20services lists various other paid services
Now don't get me wrong, I'm of course not expecting that there are commercial entities operating free-of charge list hosting services where you neither pay with money, nor your data, nor by becoming a spam receiver.
But still, in the wider context of the Free Software community, I'm seriously surprised that none of the various non-for-profit / non-commercial foundations or associations are offering a public mailing list hosting service for FOSS projects.
One can of course always ask any from the above list and ask for a mailing list even though it's strictly speaking off-topic to them. But who will do that, if he has to ask uninvited for a favor?
I think there's something missing. I don't have the time to set up a related service, but I would certainly want to contribute in terms of funding in case any existing FOSS related legal entity wanted to expand. If you already have a legal entity, abuse contacts, a team of sysadmins, then it's only half the required effort.