I have tried both of the following and still no progress
For my notification icon I am starting with an SVG with no colors defined other than white and transparent. I export the icon as a PNG with a transparent background and upload that in 48, 72, 96, 144, 192 into the image assets area of the builder.
With everything I've tried this -feels- like a bug in the builder.
I am using 3.4.5 and building an AAB
Attached is a screenshot of the problem and the the 192px version of the image I am using.