I don't know if this will work for everyone, but worked for me...
I also have the arm64 added in the EXCLUDED_ARCHITECTURES because I need it due to a project dependency.
Having it there make it possible to run my project in regular simulators (not the Rosetta ones), but apparently it doesn't work for the preview.
So I did the following:
In Product > Destination > Destination Architectures I selected "Show Both"
At the Canvas tab, in the device selector now all the devices appear duplicated. If I select the ones nearer to the bottom (yeah, specifically in this selector the "(Rosetta)" text doesn't appear) the preview works:
This allows me to use the preview and have the "arm64" added under the excluded archs.