Shouldn’t upgrade macOS until Espressif and/or Apple updates their software.
Thanks for that. I tend to wait a bit before installing these updates so these kinds of things get resolved.
esptool v1.0.5 rc4 has fixed it. See: https://github.com/espressif/arduino-esp32.
https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_dev_index.json to the Additional Board Manager URLs field to access.