Like I said in my comment, Standard picklist values are stored in the StandardValueSet metadata type.
Ensuring that you include standard picklist fields in your unmanaged package might give you the standard values as well, but I'm not 100% sure on that.
The sure-fire way that I know of is to create your own package.xml file, include that metadata type in it, and retrieve using that package.xml file via
sfdx force:mdapi:retrieve -k <relative path to your package.xml> -r <relative path to your target directory> -u <username or alias of org to retrieve from>
StandardValueSet is not one of the metadata types that supports wildcard, so you'd need to explicitly state which ones you want to pull. There is documentation that covers what the standard picklist fields are, and what valueSet name to use.
The one caveat that I've run into thus far is with
ContractStatus. For some reason, this one picklist's values contains extra information that is not captured in the
StandardValueSet metadata type. I have not found a way to deploy customizations to this field.
Some clarification for those who may not have used the old force.com migration tool + Apache Ant.
package.xml is a file that looks like this:
<?xml version="1.0" encoding="UTF-8"?>
Each metadata type that you specify is a
For most of the metadata types, we can use the wildcard to say "just give me everything of this metadata type" (that's the
"StandardValueSet" cannot use the wildcard, so each standard picklist value set that you want needs to be explicitly named
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