Still waiting for boards. Testing the Arduino Mega 2560 variant meanwhile, and it works really well. Code uploading seems reliable. As you can download too, the device is a more modern variant of the cassette tape recorder. Have to create a new python script to automate this, but the download option of a generic terminal program will work too.

A minor nuisance is that the command interpreter works with a line-feed as terminator, and terminals send a carriage return on Enter. Control-J works, but is way less convenient.