I had similar issues upgrading to marlin as well. if uploading through
repG you need to stick with v2. as v3 cannot be uploaded through repG,
at least when I tried last time about 2 weeks ago.
I had difficulties uploading through ardunio directly. compiling went
fine but the connection and upload could not be made successfully. I
am not familiar with ardunio, so for me the safe bet was to move back
to the repG pathway.
I am pleased with the results so far and will wait for future updates
before trying to update again. it is much better than the 5D for sure.
baudelaire is set to 115200