is there any way to get a list of acknowledgements (dependency, URL, LICENSE) from all the dependencies that an app has via Xcode/SPM integration?
No. That information isn't currently exposed through SPM. Hopefully something can come from the metadata support discussion currently happening, or perhaps it can be a feature of the package index sites (enter your dependencies, get a generated acknowledgement file out).
Yeah a shame :(
I found xcode checkouts of the packages in the derived that but there doesn't seem to contain anything workable.
Out of curiosity, do you know if you can get this from a package using SPM (Package.swift) directly (no xcode)?
No you can't, SPM packages have no metadata currently. Technically, since SPM does a full checkout, you could write tooling that attempts to pull the LICENSE.md file of every dependency and then build a view or put them somewhere to view.