Dear Nikolas,
I am just a user of PSPP (under Linux Ubuntu 20.04). However a few days ago I wanted to insert my data form .ods file (LibreOffice calculus) to PSPP.
Opening the data window of PSPP I went to menu File and selected the "Insert data..." Then it opens a window to guide you how to insert the whole file to PSPP.
However if you want to insert a part of the data, I suggest to split the ods file using the LibreOffice calculus program, and then insert the splitted file.
That's the way I have done it. I hope it helps.
Yours Faithfully
Kostas Oikonomou