In general, my experience says better not to update from 1803 to 1903 (even through M$@Wx is saying 1803 is to out-of-service), because many have reported issues w.r.t. BT & WiFi after the update., e.g. , , and more.
Now I got BT back but in device manager it doesn't show as DW1560, strangely like this:
how about yours look like? even with Killer card? Does it show as Killer xxx as the WiFi card name and BT name?