The answer above is correct. You don’t want to add any cache generated on a specific build or machine to the repo.
Jekyll 4 adds caching to store results of deterministic functions to make builds faster.
Cache by it’s very nature is temporary so shouldn’t be fixed and if it was it would be named something else.
Here is my ignore file built in minima and jekyll quickstart. It ignores jekyll cache, jekyll metadata, sass cache and other things.