@AmigaSociety
You could try the following....
from your AmigaOs4.1 installation "Sys:Kickstart/" take the "RadeonRX.Chip" and copy it to your USB stick in the same directory Kickstart. Next you have to edit "Kicklayout" it is also located in the Kickstart directory of your USB stick, add the following entry "MODULE Kickstart/RadeonRX.chip", preferably in the column where "MODULE Kickstart/PCIGraphics.card" is located, save and you are done. Next you could try booting the USB stick. I'm not sure if this will work, you might need more dependencies like newer kernel, PCIGraphics, graphic.library. But it's a try......
Otherwise there is also a guide here in the forum that describes how to create a bootable USB stick from a running AmigaOs4.1 installation.
https://www.amigans.net/modules/publisher/item.php?itemid=29