@th Oh, that one did exist though. I worked with that for quite some time (screenshot of OpenStep for Solaris back here, and I also should still have the installation files somewhere): https://mastodon.infra.de/@galaxis/100772106437750714). I think there was something like Sun had bought Lighthouse and wanted to publish their Nextstep productivity suite for Solaris or something like that? Never released, though.

Also, the full OpenStep 4 system was ported to sparc (and hppa) a little later on.