I'm pretty sure even OpenBSD packages OpenSSL in ports for third party software, since so many pieces of software basically require it and do not work with LibreSSL anymore.

I suppose a Linux distro could hypothetically take the same approach and use a mixture of both, but realistically most people don't want to bother with that.

Personally I'd love a Linux distro with a BSD-style base system and extra packages kept separately, but the closest to that would be ... Slackware with pkgsrc or something I guess.