Hey mate.. Sorry! I just realised you'd replied.
I imagine the crontab would look something like this:
0 2 * * * peertube import -u 'https://XXXXX' -U 'XXXXX' --password 'XXXXX' --target-url 'https://www.youtube.com/channel/XXXXX' --since $(date --date="-1 days" +%Y-%m-%d) --tmpdir /tmp
Let me know if you see anytihg weird there, or if you need any more info.
Thanks again!