Everything is converging on Linux these days, and even the majority of the people who used to promote Solaris, DTrace and ZFS, have seemingly moved on, mostly to Linux, somewhat to FreeBSD, too, per Brendan Gregg:
Solaris to Linux Migration 2017 - https://news.ycombinator.com/item?id=15177118 - Sept 2017 (129 comments)
In the BSD land, things aren't that much better, either.
Netgate, the makers of pfSense, are now using Ubuntu for Netgate TNSR product.
iXsystems, the descendants of BSDi, have moved FreeNAS / TrueNAS from FreeBSD to Linux. They're basically d/b/a TrueNAS now, and it's all Linux now.
You used to need Solaris or illimos or FreeBSD for production-ready ZFS support, but now OpenZFS is provided exclusively for Linux and FreeBSD; note that Linux already comes first in the title; it would seem like it's only a matter of time before FreeBSD support may follow Solaris and illumos.
Joyent, the commercial shepherds of OpenSolaris descendants like SmartOS, were acquired by Samsung, but the entire Solaris part of the equation, including Triton DataCenter orchestration, were subsequently offloaded to mnx.io, a tiny cloud hosting provider based out of a small town in Michigan. (Frankly, without Triton, I don't even understand what remains of Joyent at Samsung? Just the physical servers with the third-party software? It's basically just a name for Samsung's data centre ops and their presumably-Linux-based Private Cloud?)
Apple used to use NetBSD for AirPort WiFi routers, but the whole router line has been discontinued. (I thought Apple actually already dropped NetBSD but couldn't find a source right now.)
Last not least, DJB used to run OpenBSD, then FreeBSD, but then switched to Ubuntu after possibly being annoyed that too many steps were required to make FreeBSD work as a desktop: http://cr.yp.to/unix/feedme.html (my fav is that in FreeBSD the audio doesn't work unless you recompile the kernel). I think he initially may have abandoned OpenBSD because it was crashing too often for undetermined causes: http://cr.yp.to/serverinfo.html.
FreeBSD is still used by Netflix OpenConnect Appliance, which is a huge win, but feels like too many eggs in a single basket:
Serving Netflix Video at 400Gb/s on FreeBSD [pdf] - https://news.ycombinator.com/item?id=28584738 - Sept 2021 (293 comments)
But that's about it. Linux has won.