What if instead, you just store local copies of your data, possibly organized and synchronized? If necessary it can be done manually, just download anything important enough that you might want it later. If a service decays, then import it into another.
A big point the author makes is that many cloud providers don’t let you download the data. But any media that can’t be accessed outside bigco’s cloud can’t be uploaded to your cloud in the first place. If bigco’s cloud prevents you from downloading data that you create or upload, only then the solution is to use a (possibly self-hosted) alternative. However, in practice I rarely see this happening, for example downloading from Google Workspace and OneDrive is very easy (it can even synchronize a folder on your local machine), and if you’re worried about it happening in the future, again, you can backup important files.