See PM.
Yes, Amazon UK still sells almost everything to Ireland that they did sell before, stuff like seeds would be mostly blocked (should be all blocked). There are illegal sellers of seeds on Amazon UK outside of EU and UK. Mostly it's cheaper to use Amazon DE, even paying for shipping, but that ONLY applies to physical goods excluding POD. Excludes Kindle ebooks and former Createspace (which was only retail in Europe/UK, the proofs came from USA with USA shipping and time costs). Non-proof retail copies of paper books that are POD are the same as buying any other book. They are printed wherever suits Amazon, you can't choose.
Amazon/CreateSpace Proof Copies of POD paper was always from the USA. Unless the plan is ONLY to sell paper on Amazon, you are now better using
https://www.24bookprint.com/en/contact/ in Europe and Lulu in USA. There is also Ingram Spark, but they charge about $45+ per title you setup before cost of proof print and shipping.
There is a good company in Germany, but despite writing nice German to them, they will only deal with German addresses. Such physical restrictions are allowed in the EU for physical goods.