SunOS had /dev/poll, which the kqueue paper cited as prior art. https://web.archive.org/web/20000823103627/http://docs.sun.c... via citation 4 in https://people.freebsd.org/~jlemon/papers/kqueue.pdf

For a brief moment before epoll came along it looked like Linux would get /dev/poll.[1] In fact, IIRC, epoll started as a /dev/poll implementation. I don't think Sun's /dev/poll ever saw much uptake because, aside from the limitations mentioned the kqueue paper, the pace of software development was much more rapid and dynamic in the FOSS and web worlds, and the center of gravity had already shifted to BSD and Linux.

For better and worse, Linux developers seemed more inclined toward adopting extensions from SysV and SunOS/Solaris than from the contemporary BSDs.

[1] See, e.g., https://lwn.net/2001/0712/a/devpoll.php3