The spiritual successor for Sun machines is Oxide (lots of ex-Sun folks). And Sun got acquired by Oracle so it’s still technically around on the software side via virtual box and Java.
That's the point though.
What's left of Sun is basically a startup founded by a few ex-employees, some open-source software, and the rest of their IP being milked by Larry Ellison.
Neither SunOS or Solaris were open source, or based on open source.
I'm not talking about SunOS or Solaris. I'm talking about Java, dtrace, OpenZFS, and a various other random bits of Sun legacy still floating around in modern open-source systems.
I love Oxide's podcast. I checked its career page a few times but they are only hiring for field sales.