This is where the supply chain metaphor — and it is just that, a metaphor — breaks down. If a microchip vendor enters an agreement and fails to uphold it, the vendor’s customers have recourse. If an open source maintainer leaves a project unmaintained for whatever reason, that’s not the maintainer’s fault, and the companies that relied on their work are the ones who get to solve their problems in the future. Using the term “supply chain” here dehumanizes the labor involved in developing and maintaining software as a hobby.
The Linux foundation is full of major Capitalists who mutually agree to help maintain software they are dependent on. You would think that they would help in part to maintain their dependencies but why would they if it’s being maintained for free. Either way they’ll have to maintain them or find an alternative which likely doesn’t exist.