Perhaps this is still Community-consensus-needed, because I have looked a large number of users, they're still using "zh-classical (on zhwiki)" instead of "lzh (on zhwiki)" on their userboxes. By the way, on Incubator, the Wp/lzh is redirected to Wp/zh-classical (@Byfserag: ?!), which is also misleading (at least) me: users are still claiming that "zh-classical" is a valid code.

Can we add an alias rather than rename?

In T30443#3335274, @vjudge404 wrote:

Can we add an alias rather than rename?

Hmm, I still think that renaming URL is a better way, as this Wikipedia doesn't have high traffic streams and actually, no actual opposition.

Desktop:
lzh.wikipedia.org → zh-classical.wikipedia.org or zh-classical.wikipedia.org → lzh.wikipedia.org

Mobile:
lzh.m.wikipedia.org → zh-classical.m.wikipedia.org or zh-classical.m.wikipedia.org → lzh.m.wikipedia.org

In T30443#3335289, @LNDDYL wrote:

Desktop:
lzh.wikipedia.org → zh-classical.wikipedia.org or zh-classical.wikipedia.org → lzh.wikipedia.org

Mobile:
lzh.m.wikipedia.org → zh-classical.m.wikipedia.org or zh-classical.m.wikipedia.org → lzh.m.wikipedia.org

If you're asking Interwiki prefixes, that's already done (T23915 try it here); for DNS/CNAME redirecting, file a subtask and ping 1~3 random SRE members; local Interwiki links can be changed by a bot, anything else?

Any update on this? It should not be too difficult to be consistent with the ISO code, in either way we could have a CNAME from zh-classical.wikipedia.org to lzh.wikipedia.org, and avoid any potential problem.
BTW, the consensus is to use ISO code already, I see no reason to debate it on a case by case basis, this is not an extraordinary situation. A CNAME record would solve any potential problem.

T167513 is deployed, so any url changes needed on other sites for the sub-domain shfit to happen can be done.

T10217 describez other zh langs that need to renamed to conform to official IANA lang tags.

But this one has a particularly bad problem: it violates the format of lang tags. So this results in errors when parsing the WD rdf dump latest-all.nt.gz:
Error while parsing N-Triples: error while parsing language tag 'zh-classical': A subtag may be eight characters in length at maximum on line 57413752 at position 108

@Smalyshev please add some tags for Wikidata and the Query service (I'll try to do it, but not sure I have the rights)

Bart Hanssens tried to validate the WD dump with rdf4j:
https://github.com/barthanssens/rdf4j-bigfile-validator/blob/main/log.txt
'孟慶雲' was not recognised as a language literal, and could not be verified, with language zh-classical