Great news! Very quickly done, which kind-of makes me suspicious... One thing I did already observe is that I was able to send a message to a closed Gitter room via my Matrix account, although I couldn't see other people's messages.
Thanks! I'm still in the room with no feedback that sending the message failed, but from the room's point of view it's now private.
One other thing: my message was still posted by @matrixbot, rather than by my Matrix user. Is this another case of every client having to migrate (I'm using Fractal)?
If you see messages directly from `@matrixbot` in the chat area, then that means that the room is still plumbed using the old Gitter bridge. We're working on a plan to migrate rooms using the old bridge over to the new one, https://gitlab.com/gitterHQ/webapp/-/issues/2674
Are you sure it's a room issue? In the same room where my message was sent directly by @matrixbot, I can also see an earlier message from someone else from @theiraccount:matrix.org.