It's FOSS - https://itsfoss.com/linux-mint-drops-kde/
Brief: The KDE version of Linux Mint 18.3 that will be released soon will be the last to feature a KDE Plasma Edition. Which means Linux Mint 19 and above will not have KDE edition.
Linux Mint KDE Edition will soon be history. The Linux Mint Project head, Clement Lefebvre announced it in a blog post detailing the future plans of the project. He said, “In continuation with what’s been done in the past, Linux Mint 18.3 will feature a KDE edition, but it will be the last release to do so.”
This means Linux Mint 19 will be available only