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
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