I am running Ubuntu 18.04 with Jakeday's surface linux kernel on a Surface Book 2.
I had a serial connection working yesterday. I had this problem on another pi zero. I researched the "failed to set dtr/rts" issue and it seems that I need to specify device platform settings or something like this. I think the pi is not reporting itself correctly to my laptop. I had used a different pi with this recently and it was having this problem. Then I switched the SD card into this pi and it was fine. Now this pi is acting up.
Also the pi behaves just great on Windows and I can use putty to get in.
Here is the output of dmesg:
[142367.770182] usb 1-1.1.3: USB disconnect, device number 11 [142368.089461] usb 1-1.1.3: new high-speed USB device number 12 using xhci_hcd [142381.665842] usb 1-1.1.3: new high-speed USB device number 13 using xhci_hcd [142381.790983] usb 1-1.1.3: New USB device found, idVendor=0525, idProduct=a4a7, bcdDevice= 4.19 [142381.790988] usb 1-1.1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0 [142381.790991] usb 1-1.1.3: Product: Gadget Serial v2.4 [142381.790994] usb 1-1.1.3: Manufacturer: Linux 4.19.66+ with 20980000.usb [142381.796034] cdc_acm 1-1.1.3:2.0: ttyACM0: USB ACM device [142397.562400] cdc_acm 1-1.1.3:2.0: failed to set dtr/rts [142402.682581] cdc_acm 1-1.1.3:2.0: failed to set dtr/rts