Do you use the server addition  with or without deepins desktop?
Is your System using one or two network cards?
Is it a V-Server or a real machine?

Setting a Static Ip is simple by using sudo nmtui

Be aware that Network-Managers Gui component is overriding setitngs written by nmtui.. You have to use nmtui first and than check the settiings in the graphical gui to make shure, they are the same.

do not use /etc/network/interfaces.d here. The network-Manager Service will not manage these connections by default.

I got it working thanks to you. I have never heard of nmtui, but it is easy to use.