hi @JPinBe, John
Tags are somewhat difficult to understand because they can have different scopes. A tag created in a public (main) board will have a public scope. When you duplicate that board the tags are selectable as they are in any other public board in your account. So, it is not a matter of duplication it is about the scope of the tag.
What I have seen is that tags created on either personal or private boards have a scope to that board (call it a private tag). It gets confusing when you add a tag to a personal or shareable board with the same name of the tag used somewhere in a public board. Now you have 2 tags with the same name and different scopes.
When you duplicate a personal or shareable board tags will “copy over” only when you select to duplicates structure + items BUT only tags that are used in items within the source board are visible (selectable) in the duplicated board. It looks like this is the behavior you are seeing here. The tags you do see (are selectable) are those that appear in any item in your template. As far as I know there in no possibility to copy tags from one shareable board to another.
On the other hand if you use a dropdown column the values of the dropdown are copied over to duplicated boards (even if they are not used in the source board).
I hope this gives you some ideas about using tags. Always open for a chat, just send me DM for a Zoom or Teams meeting