HI!
I found a workaround by myself using my iPhone (with the latest iOS 15.6.1).
Reminder app on iOS is upgraded ... that is ... I can have all the newest features that I still don't have using an older OS on my Mac.
How did I solve my problem?
I open Reminder and I select one list.
Then I touch the three points in the upper right side of the window where I can choose the option "Print".
A new window shows other options to print the list (if I had an air print printer, which actually was not available), but I can also choose to touch in the upper right side the word "Print" and -this way- I can show a lot of other options.
So I can choose "Save on File" and I got the print of my list saved on iCloud Drive in a PDF format.
Using my Macbook I can open now iCloud drive and I find the pdf file I need (which I can use or print).
I hope this can help someone else.
Alberto