I also just tried to ssh to common-lisp.net. The host key has changed. I guess that's expected since you changed the host

Yes the toplevel common-lisp.net is now pointing to the same as future.common-lisp.net.

If you want to ssh into the legacy host, you can use any other unused subdomain of common-lisp.net, e.g. `ssh legacy.common-lisp.net`