I am not yet sure what to do with this issue. The Arduino is saying that it has an AT-capable ttyACM port, so ModemManager tries to use the port. I'd like to improve the heuristics to detect this without falling back to the blacklist, but not sure yet how to reliable do that. Ideally, the Arduino shouldn't say that its ttyACM is AT-capable...
Any suggestion on how to improve the heuristics, without falling back to the blacklist, would be appreciated. Maybe we should no longer try to use devices that expose one single ttyACM port even if the ports are reported as AT-capable?