Linux UART left in unknown state after first use flashing UPDI

[bradanlane]

Command: `pymcuprog write -t uart -d attiny1616 -u /dev/ttyUSB0 -c 115200 -f firmware.hex --erase --verify

Platform: Linux (Ubuntu 22.04.1 LTS) UART: CH340-E Target: ATtiny1616 Behavior: flash completes first time successfully; subsequent attempts fail.

pymcuprog.serialupdi.physical - INFO - Opening port '/dev/ttyUSB0' at 115200 baud (timeout 1.0s)
pymcuprog.serialupdi.physical - ERROR - Unable to open serial port '/dev/ttyUSB0'

unplugging / pluggin-in the USB-UART accomplish some sort of reset and it will work again, once.

Note: The same test under Windows 10 x64 works every time and does not require the USB-UART to bet manually reset.