This information is for:

• UK nationals and non-EEA family members residing in Ireland at the end of the
  Brexit transition period on 31 December 2020.
• Non-EEA nationals who have submitted applications (including review
  applications) to Immigration Service Delivery for residence in Ireland as a family
  member of a UK national.
• Persons who currently hold a valid EU Treaty Rights residence permission on the
  basis of relationship with a UK National.
• Non-EEA nationals who wish to join their UK national family member in Ireland
  from the 1 January 2020.

Link to full document >> Department of Justice, Immigration Service Delivery