Export Xpubkey from Bitcoin Core How do I export my HD wallet's Xpubkey in Bitcoin Core?

Do I construct it using the value of "hdseedid" returned by getwalletinfo?
It does not have one.

Bitcoin Core uses hardened derivation, so there is no way to compute the addresses it will use externally.

Support for that will likely be added in upcoming versions, but likely won't be the default (there are security risks when using non-hardened derivation).