There are some packages in the actual AUR that use the deb packages as source, extract them, and make them into something that can be installed using Pacman. So we’re going full circle now 😁
The reality that OpenOffice is dead since a decade aside and you only want to try it for experiment reasons and not for actually using it: What happens instead? Do you get any error messages? Try running it from a shell and see if you get any useful output.