For most people, moving to Ireland is the simplest move abroad there is. You need no visa, no work permit and no new language. You can start work the day you arrive.
Your belongings are the exception. Ireland is in the EU and the UK is not, so since January 2021 everything you send crosses a customs border. Used household goods still go in free of duty and VAT, but only with a declaration that has to reach Irish customs before your belongings do. This page explains how that works, how long the move takes and what it costs.
Quick answer: a removal from the UK to Ireland travels by road and ferry and usually takes one to two weeks from packing day to delivery. You will need a customs declaration (form C&E 1076) and supporting documents, sent to Revenue about two weeks before your belongings arrive. If you have lived outside the EU for at least 12 months and have owned and used your belongings for at least six, they normally enter Ireland free of duty and VAT.