If I'm not mistaken, you overlooked another role of cloud services: coordination of real-time connections between endpoints, and in some cases actual relaying o

If I'm not mistaken, you overlooked another role of cloud services: coordination of real-time connections between endpoints, and in some cases actual relaying of data to work around NAT. I guess this is the space you're in with ZeroTier. But I'm not sure how much of a market there is for generalized solutions like ZeroTier and Tailscale. For the most part, people want solutions that connect their machines for a specific purpose, such as remote desktop access (e.g. TeamViewer/AnyDesk), and developers of such products don't want to require their users to have another networking product (ZeroTier/Tailscale) first.