I’m aware of the issue in NFS package and I need to admit that it is kinda complicated. There was a PR, which was no way tested on OpenWrt 18.06 and since 8 May it is broken. The maintainer suggested to everyone in this issue that if anybody cares about that you are welcome to send patches, which in my point of view is wrong. Those changes should be reverted, I found that I have prepared those changes in my branch, but didn’t send them yet as I didn’t test it. Most probably I won’t be able to test at it soon and don’t want to promise anything, what I can fulfill. If there’s anything new, it will be mention in release notes.
About samba4, it is a little bit complicated. I described it in the Czech section as there was a similar discussion. I was asking devs of OpenWrt main repository, why there is not still samba4 in the stable release a few months ago, it requires to update updates of various packages due to switch from librpc to libtirpc. OpenWrt 18.06 is feature frozen and should receive security & bug fixes. The next version of OpenWrt 19.07 was branched off months ago, however, no sights of RC. In my point of view, it makes sense to wait for it as there you can find samba4 with a lot of new features and packages if you would like to try it, you can by using switch-branch, but things can be broken as it was not released and thus not tested properly.
It does not mean that we don’t accept pull requests (patches) to our Turris OS, where you can add samba4 if you want, but it comes with responsibility.