Vielleicht hilft es jemandem:
Ich hatte das Problem, dass der Serial Port immer direkt wieder verschwindet.
dmesg hat so etwas in der Art ausgespuckt
[ 738.365561] usb 1-10: new full-speed USB device number 8 using xhci_hcd
[ 738.607730] usb 1-10: New USB device found, idVendor=1a86, idProduct=7523, bcdDevice= 2.64
[ 738.607737] usb 1-10: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[ 738.607739] usb 1-10: Product: USB Serial
[ 738.619446] ch341 1-10:1.0: ch341-uart converter detected
[ 738.633501] usb 1-10: ch341-uart converter now attached to ttyUSB0
[ 738.732348] audit: type=1130 audit(1632606446.974:2212): pid=1 uid=0 auid=4294967295 ses=4294967295 msg='unit=brltty-device@sys-devices-pci0000:00-0000:00:01.3-0000:03:00.0-usb1-1\x2d10 comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
[ 738.768081] audit: type=1130 audit(1632606447.007:2213): pid=1 uid=0 auid=4294967295 ses=4294967295 msg='unit=brltty@-sys-devices-pci0000:00-0000:00:01.3-0000:03:00.0-usb1-1\x2d10 comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
[ 738.776433] usb 1-10: usbfs: interface 0 claimed by ch341 while 'brltty' sets config #1
[ 738.783508] ch341-uart ttyUSB0: ch341-uart converter now disconnected from ttyUSB0
[ 738.783521] ch341 1-10:1.0: device disconnected
[ 739.955783] input: BRLTTY 6.4 Linux Screen Driver Keyboard as /devices/virtual/input/input35
Dieser Beitrag auf Stack Exchange hat mir geholfen mit folgendem Befehl.
sudo systemctl mask brltty.path