What are the travel rules for EU citizens with (pre-)settled status travelling between the UK and Ireland, Isle of Man, Guernsey or Jersey (the Common Travel Area CTA)?
You will not pass through any immigration control when you enter the UK across the land border between Ireland and Northern Ireland, so you don’t need any documents to enter the UK on that route.
However, you may be asked to show your passport (which should be valid for the whole of your stay) or identity card to enter Great Britain when travelling from Ireland if you are encountered by Border Force.
You should ensure that your ID card is linked to your EUSS status, in order to travel with it - you can do this here: https://www.gov.uk/update-uk-visas-immigration-account-details. See this FAQ and this FAQ for more details, including what happens if you try to update the status but the update has not yet taken effect.