[Affected versions]
Release 77.0 (64-bit)
Beta 78.0b5 (64-bit) (64-bit)
Firefox Nightly 79.0a1 (2020-06-10) (32-bit)

[Affected platforms]
( macOS 10.14 (Mojave))

[Steps to reproduce]

1- Launch the Firefox Browser and open an online editor https://docs.google.com/spreadsheets and also open installed app (libreoffice)
2- Create a table in online editor spreadsheet
3- Select non-consecutive rows and copy
4- Paste it in the same sheet or installed app.
5- Rows are pasted one on top of the other (it doesn't matter how many rows were in between that were not copied)
6- Now create a table in installed app.
7- Select non-consecutive rows and copy
8- Paste it in online editor.

[Expected result]
Selection should be pasted accordingly.

[Actual result]
Notice that i'm unable to copy non-consecutive rows from libre office to online editor. Only one line is copied.

(Notice this is different from https://bugzilla.mozilla.org/show_bug.cgi?id=1640856 since the selection matches the length of each row selected

This issue is reproducible on Nightly 80.0a1 (2020-07-22)(32-bit). I'll change flags accordingly.

Reproduced this issue on Firefox 80.0b6 under Windows 8.1 on Google drive spreadsheet.

That's a bug of LibreOffice Calc, it only exports the first row to the clipboard.