It turned out it was just a mismatch between the reaper_plugin_functions files with the older Linux installation, here's a link to the project...
https://mega.nz/#!ipMjXCSY!MWF5Cs7Io...so1MgxKBCT9YVY
You can Open Folder in VS2019, select the CMakeLists.txt file as the Startup Item and build directly from there (or just use CMake normally).
For Linux builds using VS2019:
- install openssh, build-essential, cmake 3.11 on remote Linux
- run "sudo service ssh start" after logging on to Linux
- in VS, add the remote Linux machine up in Tools->Cross Platform
Now just select Linux-x64-Release (or Debug) from dropdown in VS to build.