If change addresses are not automatically recovered from a backup, that seems like a serious bug/shortcoming in Bitcoin Core to me.

A couple of questions.

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Remember you MUST have the public keys available to you (you can find this in the explorer, ...

You write that you need the public keys, but the instructions never use them. When you wrote "public key", did you mean "address"?

How do you find the public keys (or perhaps addresses) generated by the wallet in an explorer?

If change addresses are not automatically recovered from a backup, that seems like a bug/shortcoming in Bitcoin Core to me.