GHE (Server) 上のGitHub Actionsではactions/cacheは何もしない
action/cache is currently not supported on GitHub Enterprise Server.
https://github.com/actions/cache#known-limitation
saveしない
https://github.com/actions/cache/blob/611465405cc89ab98caca2c42504d9289fb5f22e/src/save.ts#L14-L19
restoreしない
https://github.com/actions/cache/blob/611465405cc89ab98caca2c42504d9289fb5f22e/src/restore.ts#L9-L15
GHEかどうか判定するロジック
https://github.com/actions/cache/blob/611465405cc89ab98caca2c42504d9289fb5f22e/src/utils/actionUtils.ts#L5-L10
ロードマップはある
Cache support on GHES · Issue #273 · github/roadmap