Nebula seems to be under Defined Networking (https://www.defined.net/) now. It lacks the ease and tooling of the multitude of others that emerged in the space. My gut is that it's usable for the clever home user but meant for a professional IT dept with the ability/desire to build their own tooling and automation around it. The spartan mobile app is a sign of such. Tailscale is probably more easily usable for the average user than nebula or even vanilla wireguard.