I’m afraid I have no experience with Docker, and don’t know what to do with a dockerfile. But in any case there is a limit to how far I can go to replicate issues in the field; generally I’d only get involved if the problem can be replicated with the core.
The raw source of the prerelease is available on GitHub at https://github.com/Jermolene/TiddlyWiki5, and there’s a prebuilt version at https://tiddlywiki.com/prerelease.