Many thanks for the help & pointers. (I leave this here for others to find, IMHO it would make sense to include in the Building.md file but that’s not my decision.)
It looks like VS only installs parts of nuget, not the CLI command, so you need to Install nuget.exe from the nuget web site (put it in the VS…/msbuild…/bin dir so its on the path).
Open a “X64 native tools command prompt” (on the Start menu in visual studio tools).
run these commands–
cd casparcg\server (the server top-level dir)
nuget restore “build\CasparCG Server.sln”
msbuild /val “build\CasparCG Server.sln”
msbuild /filelogger /detailedsummary /p:Configuration=Debug “build\CasparCG Server.sln”
Ten minutes later I had a debug build (with no errors/warnings). Haven’t tried running it yet.
Mingw- I use it because the shell is a lot more friendly to me than CMD or powershell, it runs all the usual *nix commands, and it makes windows-native executables. It’s also a lot more light-weight, in general, than VS. Given that there is already a lunix build, in theory mingw should be able to build the server, and probably scanner, with minimal changes… I’ll try that in my copious spare time. (building the client is a good question,. but mingw and qt get along nicely.)