As a FOSS developer I wish I could notarize it without paying $100/year to Apple.
"One day," Apple could do anything. One day, they could totally prevent installing things that are not notarized. One day, they could entirely prevent non-AppStore, non-sandboxed applications from running on macOS. They haven't, but they could and indeed all signs point to these being on the very long-term roadmap. Does this mean you stop writing Mac apps today?
This has in fact happened: https://blog.charliemonroe.net/a-day-without-business/