There is an installation-manual right on their site:
The removal of the motherboard itself shouldn't be any different than from the previous versions.
I have today been told by my supplier that the Akasa Newton S6 was manufactured on the basis of information that Intel provided at the pre-production stage, but that Intel changed some of the details of the NUC6i5SYK between pre-production and production, which means the NUC board is not compatible with the Newton S6 case for the current design - so I had to RMA return the fanless chassis, and am now awaiting the replacement which will take time since Akasa now needs to redesign and re-manufacture the Newton S6 so that it is compatible with the NUC - sigh!
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Regarding the disassembly of the unit or removal of the motherboard, it has pretty much the same design as previous versions, so any video tutorial online will help you on that task, just be careful of not pulling inappropriately cables /components connected to the unit, to avoid any possible damage.
I am sorry to hear the issue with the pre-production design and the fanless case to be used, hope you get the replacement soon.
If any additional questions or inquiries are present, feel free to contact us back.