I'm sorry, but it is nearly certain Lockdown will never be installed at any Wikimedia wiki. MediaWiki is a complex application that was never written with regards to per-page or per-namespace read restrictions and there are probably a lot of ways those restrictions can be theoretically (or practically bypassed). I think we should not have any such options available, rather than relying on them (and being surprised when someone figures their way around).

To share some context, a serious security vulnerability was recently found in MediaWiki core that effectively allowed everyone to read any pages on (some) private wikis, see https://www.mediawiki.org/wiki/2021-12_security_release/FAQ for related security announcement. Reviewing all of MediaWiki (and relevant extensions) and fixing it to be certain no information can leak will unfortunately take a lot of people's time, and I don't think there's any plan to do that kind of work in foreseeable future.

Because I consider it nearly impossible for the necessary work to be finished in the foreseeable future, I'm declining this request.

Italian Wikipedia requested https://sysop-it.wikipedia.org to be created for sysop coordination (T256545), which might be a better option (and one that's more likely to have). @Ladsgroup might have an opinion on this topic.