Gregory's Server
What about XMPP MUCs that bridge with Matrix?
Well, they get archived as well...: https://github.com/matrix-org/matrix-public-archive/issues/47#issuecomment-1574978098
It's seriously a very neat product as a piece of software, it's very cool, but its rollout is just absolutely anti-community and user hostile, if not sometimes dangerous.
For clarity, this can affect your channel if "Members only (since the point in time of selecting this option)" or "Anyone" is selected, as far as I know.
A moderator* in the channel also has to publish an alias in the room directory of a server that federates with matrix.org to eventually join your room on demand (as soon as someone requests it) and publish the chat logs under that domain.