The FCC has released an announcement that all FCC filings due between October 1 and November 17 (Monday) are now due Tuesday, November 18. You can read the notice here:
The FCC may release additional announcements of further extensions for specific types of filings, which in past shutdowns has largely meant that it would monitor its filing systems to see if any collapse from the massive number of filings, and then grant further extensions for filings that must be made in the failed system.