select2 - use as autocomplete textbox (even if not an option)

I'm trying to use the select2 add-on as more of a textbox (compared to a dropdown) with autocomplete features. This means that if a user types something that is not in the list, I want this custom value to remain as the value for the form.

I've searched stackoverflow and found the following:

Disable "No matches found" text and autocomplete on select2

Select2, when no option matches, "other" should appear

Neither of them keep the "custom" value.