I've actually implemented NFS servers professionally (for my sins) and used various competitor implementations. It's possible with the mechanisms others have mentioned, but ultimately each vendor has its own specific ways to circumvent the "Kerberos is annoying and often not well configured at the client" issue[0]/allow various 'hacks' to be deployed, so if you're interested in a specific vendor's product (e.g. ONTAP) the best option is to look through their online manual for the specific CLI/Web GUI features, usually around root squashing and the like.
[0] I actually really like it, but the reality and customer feedback is what it is...
In what way are implementations not inter-operable? The SunOS and Linux implementations, at least, coexist happily (modulo ACLs). Do others fail to implement the standard?
1. There aren't many NAS devices that gracefully interact with both Active Directory and Kerberos (if you care about that, for both SMB and NFS access to the same storage). The best that I know that is still commercially available is ONTAP (I was not employed by them, but a competitor). I don't know much about its internals, but was impressed with the features, team, my own play with it, etc.
It's also the most expensive. If interoperability with AD is not an issue, then disregard.
2. Mac OS X support for NFS v4 and its variants is abysmal. To the point that I could craft packets that would cause a reboot on the latest OS (which to me yells probable 0-day... but hopefully fixed since then and security analysis is not my expertise). Their SMB client is really good though, second to Windows in terms of keeping up with features, using them correctly, etc.
3. What's the use case for the mobile devices? The NFS/SMB clients I've seen for mobile are clunky as hell, but it was also never my focus.
While still only my opinion, this is true up to early 2017. I've since moved to another industry and don't actively research it anymore.
I've used krb5 and nis in an osx environment with NFS as file store. My basic opinion is that osx is not about unix legacy and they move as desired. Running on osx is agsinst a moving target.
[0] I actually really like it, but the reality and customer feedback is what it is...