Failed to commit transaction (conflicting files)

[Alfy]

please see this post from teh update thread

[Stable Update] 2020-08-28 - Kernels, Systemd, PAM, PAMBASE, KDE-git, Deepin, Pamac, Nvidia 450.66, LibreOffice 7.0

remover or rename dunstify. Or use --overwrite /usr/bin/dunstify when you update.