The Linux kernel contains both NFS and SMB clients – so in that sense, supports both equally "out of the box". Whether either or both are compiled-in (or available as loadable modules) will depend on the distribution.
Windows has an NFS client, but it is an additional OS feature which isn't installed by default (and I believe its NFS version support is somewhat outdated?)
Whether Linux distributions install the NFS and/or SMB client support by default, or require an additional package install for either or both, is really going to depend on the distribution (and its installation options)
FreeBSD, NetBSD and Illumos also include SMB client support, but I don't know how easy it is to use them as compared to their NFS clients. (From what I understand, OpenBSD pointedly has first-class support for NFS but not SMB: NFS has an in-kernel client, for SMB you have to use a user-space NFS-to-SMB translation daemon, which is in their ports tree.)
> Windows has an NFS client, but it is an additional OS feature which isn't installed by default (and I believe its NFS version support is somewhat outdated?)
Windows has both NFS server and client. It's not enabled by default, but it can be enabled. It has supported NFSv4 since Windows 8.
> Things that support SMB out of the box: Windows, Mac, Linux, FreeBSD, NetBSD, illumos
> Things that support NFSv4 out of the box: Windows, Mac, Linux, FreeBSD, OpenBSD, NetBSD, illumos
OpenBSD is the only real difference here. (And if "install something from ports" counts as "out of the box", there is no difference.)
There is still somewhat of a difference in ease-of-use though. For NFS, Windows users have to enable an OS feature which is not enabled by default. (I suppose one could automate that in the installer, run a PowerShell script for example.) Not sure how true that is for other platforms.
It still raises the question of why one might prefer NFSv4 vs SMB.
Windows has an NFS client, but it is an additional OS feature which isn't installed by default (and I believe its NFS version support is somewhat outdated?)
Whether Linux distributions install the NFS and/or SMB client support by default, or require an additional package install for either or both, is really going to depend on the distribution (and its installation options)
FreeBSD, NetBSD and Illumos also include SMB client support, but I don't know how easy it is to use them as compared to their NFS clients. (From what I understand, OpenBSD pointedly has first-class support for NFS but not SMB: NFS has an in-kernel client, for SMB you have to use a user-space NFS-to-SMB translation daemon, which is in their ports tree.)