I had this same issue. I fixed it by going to the top menu and selecting “Help” then select “Restart in safe mode”. A new window will pop up, select the white circle to the left of “Reset to Factory Settings” then directly below that select “Reset settings and user interface modifications” and “Reset entire user profile”. Click the bottom right button labeled “Apply Changes and Restart”. Open Office Libre again and the printer notification should be gone.
Didn’t work for me. On my first attempt I left windows set to “Manage my default printer”. I got the dreaded printer connection message immediately upon Libre office opened after doing the factory reset.
On my second attempt I disabled windows management, and forced the “Microsoft Print to PDF” as default. Then did the LibreOffice factory reset steps again. That time I didn’t get the message immediately. But I still get it every time I open an existing document.
The second example fits with BenMees’ analysis that the document itself stores an an expected printer.
Interestingly. When I try to go to File > Printer Settings, I get a “No default printer found. Please choose a printer and try again” error message from Calc, with no immediate open given to do said choosing. After trying a few existing docs, printing to the Microsoft Print to PDF printer, followed by updating and saving the spreadsheet contents, it seems to fix the issue for selected files. Overall, I don’t think resetting the profile had any effect.
Little follow-up on that. The default Calc profile is to “load printer settings with the document”. Factory resetting reset that.
After turning that off, when I go into File > Printer Settings… it shows my the Microsoft Print to PDF printer, regardless of whatever prior printer I used on that file.
So perhaps the profile reset did work - as disabling the “Load printer settings with the document” didn’t previously work for me.
This still feels like just a hack though. I think that driver fix is probably the best one - will try it later.