There is some confusion about Meadows "flipping."
https://abcnews.go.com/US/chief-staff-mark-meadows-granted-immunity-tells-special/story?id=104231281
Immunity is something else: This means essentially that he was forced to testify.
It works like this: If the DOJ gives use immunity, nothing he says can be used against him, so it's no longer possible to invoke the 5th Amendment.
(It's late so I'm not sure I explained it well.)
https://www.justice.gov/archives/jm/criminal-resource-manual-718-derivative-use-immunity