Sebastian,
As the shepherd you're expected to motivate your decision (typically with a summary of the proposal) to guide us toward a collective decision.
For the record, in this case, the change is that all characters considered as `newline` by the report (\r, \n, and a couple others) from the file's text are replaced by a single `\n` in a multiline string. This isn't what the current implementation does, if I understand correctly. But GHC 9.12 isn't released, and I think that Brandon considers the current implementation to be a bug, because his motivation for the design is to match what `unline . line` does.
I have absolutely no opinion on whether keeping \r\n or converting to \n is preferable. So I'm happy to defer to Sebastian.