I did an upgrade from kernel 5.4.0-74-generic to 5.4.0-77-generic and the problem disappeared.
$ stty -F /dev/ttyACM0 speed 57600 baud; line = 0; eof = ^A; min = 1; time = 0; -brkint -icrnl -imaxbel -opost -onlcr -icanon -echo -echoe -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1931684 Title: cdc_acm: acm_port_activate - usb_submit_urb(ctrl irq) failed To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/intel-microcode/+bug/1931684/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
