Made a fresh reinstall of Kubuntu 18.04 (previously I had Kubuntu 16.04 on my primary desktop). Everyting works, drivers were detected (including nvidia). Multiscreen setup works, no DPI problems, fonts are clear, performance is better. Default plasma setting are way better than 16.04. Experience is very smooth. Disclaimer: I'm not using sleep/hibernate, so no comment there.

BTW: it seems that most of binaries are being build as PIE, which also becomes the default mode for gcc (-pie/-no-pie).