Implementation-wise, didn't Solaris adopt dtruss (dtrace-based truss) as truss at some point (and thus Illumos)?
(dtrace userland is a library; you can, if you so choose, write your own tooling there. The command is "just a wrapper", a lot of similarities to bpftrace on Linux)
(can I be forgiven since I haven't really touched anything Solaris-ish for near 15 years ?)