I now believe this problem is not specific to LibreOffice. I see it there often since I use LibreOffice Writer a lot, but it just happened again when I cut some text in Geany (a text editor) and attempted to paste it into the email program Geary. So I think this is a general clipboard problem in Ubuntu 19.10.
Given that, I will change the bug's title to remove the word "LibreOffice", and remove it from the libreoffice project.
I now believe this problem is not specific to LibreOffice. I see it there often since I use LibreOffice Writer a lot, but it just happened again when I cut some text in Geany (a text editor) and attempted to paste it into the email program Geary. So I think this is a general clipboard problem in Ubuntu 19.10.
Given that, I will change the bug's title to remove the word "LibreOffice", and remove it from the libreoffice project.