One question that might be pertinent: if relying on external third party services for transport, are such services open or closed source?
For example, in my case, I use SyncThing as the transport layer for the data-based mind-scanning operation. So none of what is actually transferred actually enters the main internet, outside of devices you’ve specifically chosen to hook up with it.
But if such a service is reliant on say, a public NextCloud the situation might be different. Not really sure how to resolve that issue.
My service is meant as a more private alternative to say…Lifenaut.