2021 Edition. This is a continuation of the previous two threads which can be found here:
https://news.ycombinator.com/item?id=22299180
https://news.ycombinator.com/item?id=13660086
Other resources:
https://github.com/danistefanovic/build-your-own-x
https://github.com/AlgoryL/Projects-from-Scratch
https://github.com/tuvtran/project-based-learning