Mine works without the charging cable plugged in but once there is power to the USBc to hdmi adapter or to a powered hub I can't get it to work. It used to work maybe 5 releases ago. Before you might have had to unplug the power cord and plug it back in again at times but it would work. I think you have same issue since it seems to be a powered hub. Have you tried with no power cord connected? I also can't tell the phone what to do to connected usb devices anymore like I used to be able to. They are just greyed out.I was going to post about this today. I have this powered HDMI hub: https://www.amazon.com/gp/product/B07HNXRX5T/
I am able to get my stock V20 (Oreo) to mirror to a TV as well as get charged. On this ROM I can't get any video out. Not even with a USBC to USBC cable to a portable monitor (no hub, just phone to screen). It works fine on stock 8.0.