@8johnr8 @craiggrannell
Umbrel looks pretty cool, thanks for bringing it to my attention.
I'm going to get a little technical.
The killer feature of sandstorm.org, in my not especially humble opinion, is that it uses CapNProto (a serialization protocol invented by the same person who created the open source version of Google's Protocol Buffers v2) for application instance sandboxing and ownership. So first, an attacker has to get through the application itself and then the sandbox before they can attack the host operating system. Second, you can have multiple user accounts on a single Sandstorm server and they can share app instances with each other at will but everything defaults to private.
Separating applications into individual Docker containers, which is what I presume Umbrel and yunohost.org does, provides a kind of sandboxing. But managing multiple users and sharing between users is more complex.