As stated, really- have reinstalled system and previously flash has been easy terminal install for this relative noob- but, now, the terminal approach fails and from reading others travails seems i need to add the canonical repository, but- i do not know the address for said repository. (firefox on lubuntu cosmic, freshly installed and updated...)
flashplugin-installer is in the
I do not know the method for doing this in 18.10 Lubuntu, but enable the
multiverse repository and refresh the sources.
In stock Ubuntu the selection is here: