My computer cant find "https://downloads.arduino.cc/packages/package_index.json"

Well, drat. I tried versions all the way down through 2.0.5 and they include a dynamic library that was built for MacOS 10.15 and newer. I’m on 10.13.6 and can’t upgrade this iMac any further.

Version 1.2.3 doesn’t have support for my new board, the SparkFun LoRa Thing Plus.

Does anyone know if its possible to build the 2.2.1 Apollo3 boards library on MacOS 10.13? I see that the Arduino IDE 2.1.0 is only supported on MacOS 10.14 and newer.

May be getting time to install Linux on this iMac, but would love to hear any other ideas.