Well, if you ever have the time to give it a try..
Alpine is the most OpenBSD-like Linux distro I've yet to see. Of course, it's still not OpenBSD.
What about Void? It even used LibreSSL out of the box for a while.
I'm not super fond of rolling releases. It always feels weird when people recommend Arch or Void to an OpenBSD user. OpenBSD has very nice releases with a tested & documented update process between each.
OpenBSD has the -current branch, which is actually a rolling release
And one of the most common pieces of advice I've seen for desktop OpenBSD is to use -current . I don't on desktop because I haven't needed to, and wouldn't want to on a server though.