SB is Linux specific(actually even only a few Distro specific such as Debian/Centos flavors) as there are tabs like "Packages" which are very dependent on what package manager is used. There's also functionality for managing Systemd services and I'm not sure if Systemd's being used by other Unixes.
In theory, the app can work on any Posix compliant Unix box and have fallbacks for tabs/sections where functionality is not implemented. However, this would require quite a bit of testing overhead. My current test suite matrix for a bunch of VMs with different auth methods already took quite a bit of effort to get working. I'm not sure I'd be able to ship new features/fixes quickly if the supported OSes list increases, at least for the time being.
In theory, the app can work on any Posix compliant Unix box and have fallbacks for tabs/sections where functionality is not implemented. However, this would require quite a bit of testing overhead. My current test suite matrix for a bunch of VMs with different auth methods already took quite a bit of effort to get working. I'm not sure I'd be able to ship new features/fixes quickly if the supported OSes list increases, at least for the time being.