How to make an app behave the same way with screen off, as with screen on?
So, the only way I have found yet, to stream music to a DLNA device with screen off, using these apps, is to disable Doze mode by using this command in terminal:

dumpsys deviceidle disable


followed by dumpsys deviceidle enable when I no longer need streaming.

Now just need to find the way to automate this with tasker.