Dear Svanhvít,
Thank you for your question! In general, we are having the guidelines independent from the general MT task, you can find them
here (the input data and the output format descriptions), as well as the full guidelines for submission
here.
Related to your question specifically: no, we do not have such requirements about the newlines, because the outputs are submitted in the JSONL format and a single segment is embedded unambiguously as a value of a source or target key.
Feel free to reach out if you have more questions!
Best,
Kirill Semenov,
UZH