I can't find any of the previous dozen tax return that I have filed with Intuit / TurboTax. How can I find last years return?

Well, if you saved it as a PDF it as a PDF it should be in you computer in Acrobat Reader.  I saved mine there
and I also kept my disc for the last fifteen years and I could put that in and pull it up.

Yes, but new computer.

Did you use TT desktop to prepare them, or TT online?

Did you save your important files on a flash drive before you let your old computer go.  If yes, I guess you will have to contact help at Turbo Tax itself if you can find their phone number somewhere.