According to this blog post, https://blogs.technet.microsoft.com/wsus/2016/01/22/for-those-on-wsus-3-0-sp2-or-sbs-2011/ it should be possible to migrate the WSUS services from the SBS 2011 server to another member server, so that the latest WSUS can be used and allow servicing for Windows 10 domain members. Another TechNet article (https://technet.microsoft.com/en-us/library/hh852339.aspx) details how to do the migration, but what additional steps are needed in the case of SBS? For example, the SBS console application has an area to review / approve updates. Would that simply be ignored moving forward, or is there additional configuration needed so SBS knows it is no longer the WSUS server.
SnapOverflow
Somewhere in one of your Group Policies is a setting that directs your clients to a particular WSUS server. You need to find that setting and change it there.
I've done the migration according to the documentation from the links in the question. I did not uninstall WSUS from the SBS server, but I did disable the relevant services in the Services control panel, and used group policy to point member computers to the new WSUS server. This seems to be working fine. The SBS Console's Updates tab shows errors trying to determine update status, but I expected this would be the case.