Oh shit this makes me so happy. Dúchas is a fantastic website. If you'd like to see some manuscripts, I'd highly recommend ISOS (https://www.isos.dias.ie/
) and I used archive.org a lot while studying folklore, it actually has a lot of rare books that I struggled to find in the library. Colleges also have great information online for example:UCC https://celt.ucc.ie/index.htmlUCD https://www.ucd.ie/irishfolklore/en/TCD https://digitalcollections.tcd.ie/home/
That's all I can think of for now. Might link some relevant books as I find them on archive.org later.