Ironically, several folks who worked on Plan 9 later worked (or continue to work) at Google, although none of them worked on Fuchsia.
<ramble>
To me the major overlap between them is their designs are clearly informed by the contemporaneous shape of network architectures. Fuchsia is a take on what an OS design would be as a set of named microservices that can be routed. Plan 9 noticed network topologies of compute labs and clusters weren't too different, and both graphs could be represented in filesystems. The major visible difference to me is that the visibility of routing is much more apparent in Plan 9 than it is in Fuchsia. It's still a little difficult to understand how and where capabilities propagate through the system.
Implementation-wise, FIDL is a much different take than 9P2K. Though much simpler, 9P2K forces every API to exist via a filesystem interface (many of the higher level protocols also involve quite a lot of string passing) and struggles with throughput of streaming operations. Individual FIDL APIs might have similar problems, but the message encoding itself is relatively more efficient.
</ramble>
That’s fine as long as it’s open source and a self-contained local piece of software (as Fuchsia is). The problem with Google killing products is that they’re closed source and/or require huge server resources and/or ML models.
Operating Systems are not a very well defined subject. Linux doesn't include a UI layer for instance and that isn't considered a problem. Being tied to a particular experience limits the potential applications of the OS, so in many ways I would consider the lack of opinionated experience a good thing.
There is now a UI experience available as part of Fuchsia in the workstation product, but I wouldn't overly index on it as it's just one take on what you could use Fuchsia to build.
Google's proclivity for aggressively wiping the spaghetti off the wall is starting to work against it. I think maybe they need to start promising to open source any products they lose interest in.
<ramble> To me the major overlap between them is their designs are clearly informed by the contemporaneous shape of network architectures. Fuchsia is a take on what an OS design would be as a set of named microservices that can be routed. Plan 9 noticed network topologies of compute labs and clusters weren't too different, and both graphs could be represented in filesystems. The major visible difference to me is that the visibility of routing is much more apparent in Plan 9 than it is in Fuchsia. It's still a little difficult to understand how and where capabilities propagate through the system.
Implementation-wise, FIDL is a much different take than 9P2K. Though much simpler, 9P2K forces every API to exist via a filesystem interface (many of the higher level protocols also involve quite a lot of string passing) and struggles with throughput of streaming operations. Individual FIDL APIs might have similar problems, but the message encoding itself is relatively more efficient. </ramble>