A difference is Google versus Microsoft because Microsoft finally built it for themselves and is more generous (at least in this instance) in sharing the wealth

A difference is Google versus Microsoft because Microsoft finally built it for themselves and is more generous (at least in this instance) in sharing the wealth back to the open source community? Chromium has had open source ARM builds, build pipelines, and CI/CD for a while now since the Edge team made it a priority. Google had no interest in proper ARM builds for desktop Chromium because they didn't want competitors for ChromeOS, so almost all of that has been Microsoft engineers (or so the GitHub statistics indicate). Electron can just reuse all the work that the Edge team already did for ARM on Windows, as opposed to building Chromium entirely from scratch as they would have had to for the original WinRT era.