Just wanted you to know. . . .
On a clean install of Ubuntu 18.04, it installed LO 6.0.3, and all of the toolbars did not show any icons properly.
I found out that the icon set was installed as Breeze Dark. So, changing it to Tango made it work. Even after purging LO from that system, and then installing the latest 6.0.4, still had that problem. Was "Breeze Dark" the default icon set of LO 6.0.x? or was something else in the mix to cause the problem[s]?
My head scratching issue was why was this set to Breeze Dark and that it was corrupted.
ALSO, there was problems with the font install issues that happened to 3 clean install of Ubuntu 18.04. So, there are a lot of issues to deal with.