I found a very little information on this matter. What is the difference between dereferenceable and non-dereferenceable URIs? What does it mean to dereference a URI? How does the URI change after it has been derefenced?
When reading about linked data at Wikipedia, it is said:
Use HTTP URIs so that these things can be looked up (interpreted, "dereferenced").
This makes it sound like every individual that can be found with the HTTP URI, eg "can be looked up" can be dereferenced? But not all URIs are derefenceable.
The simple answer is that if you can fetch a resource behind a URI by using exactly that URI, that URI is dereferenceable. This formulation means that only URLs are (potentially) dereferenceable and URNs aren't.
An extended definition is that all URIs you can map to a resource can be considered dereferenceable. For example, if you can map the URN urn:isbn:0451450523 to a book resource, then you may stretch the definition of dereferenceable URIs to include such URN (I wouldn't).
While on the topic, I think it's far better to mint URNs when your Linked Data resources are not dereferenceable (e.g. using an OBDA tool like Ontop) as to not confuse the consumers.
If you are looking at a quick way to make Linked Data resources dereferenceable, you can look at Pubby (unmaintained since 1/2021) or LOD View.