So I think I found the solution, and as is often common it’s a case of RTM (Read The Manual). I somehow missed the line about “Follow the README.txt in the Modifications folder to modify Update.h in your ESP8266 core files.”
I figured that out after digging through the logs and finding the specific error message:
C:\Users\<username>\Documents\Arduino\libraries\OpenGarage\main.cpp:711:12: error: 'class UpdaterClass' has no member named 'reset'
Update.reset();
^With that done it compiles correctly. I’ll try flashing it to the board and see if I can get this running. Thanks for all the help.