Installation of the new version of LibreOffice (7.0.3-2) with language packs from AUR repositories:
The version (as far as I remember) 6.4.0 is installed from the official repositories by default.
After displaying the available version, select the appropriate packages, eg 1 2 63 121 - check carefully. And we approve.
The scary version conflicts message will appear “Do you want to delete? Yes.”
… and the result from the console
Build folder: /home/christophe/.cache/yay ==> Do you want to remove all other AUR packages from the cache? [Y / n] vol removing packages from AUR from cache ... ==> Do you want to delete ALL untracked AUR files? [Y / n] vol removing untracked files from AUR cache ... Removing debtap-3.3.1-1-any.pkg.tar.xz Removing debtap-3.3.1.tar.gz
… it takes a while but gets installed from these rebuilt packages.