Have you tried sudo systemctl poweroff ?

Systemctl is for systemd, and for OpenRC is rc-update.
I don't find in config of Deepin place where I can change that command.

To get working Manjaro Deepin I used a few tweaks.
I'm using fish shell, and added "pulseaudio --start" and "setxkbmap " to config.fish.
I installed networkmanager-openrc and ufw after system installation.
Fish is starting when Deepin starts, I added to ~/.config/autostart "fish" command.

If you don't have pulseaudio, menus of Deepin are very slow working.

I like Deepin, it's very beautiful, have some bugs but I'm using Linux from long time (from KDE3).

Yes Deepin is very unique and elegant. Keep in mind that this community forum deals primarily with the main Debian based version. There is a section in the Manjaro community forum that handles the Deepin in Manjaro.

Problem is with all Linuxes based on OpenRC.
org.freedesktop.login1 generate problem with nonresponsive button of power off.
On Consolekit2 is org.freedesktop.consolekit.system , but Deepin can't automatic change between this.

From what I understand OpenRC its a dependency based init system that originated from Gentoo. Maybe there wiki has more information ?