Debian Buster - serial issue

Not sure if this is the issue, but in Linux everything needs it's permissions, even serial ports, or more clearly, the user needs access rights to serial port.
Whenever i bump into access denied or port not found on Linux, i search for arduino as more people use them hence easier to find, so try adding you user to dialout group, so here is a link to several options, from how to find the serial port in use to setting permissions for it:
forum.arduino.cc/t/permission-denied-on-dev-ttyacm0/475568

Mud wrote:

If I'm understanding correctly it already had the permissions:

crw-rw---- 1 root dialout 188, 0 Oct 30 17:48 /dev/ttyUSB0

crw-rw-rw- 1 root dialout 188, 0 Oct 30 17:48 /dev/ttyUSB0

Those are for user root and group dialout.
You have to add your user name to dialout group.

For QtPlasmaC you need python3-serial.

Edit: For a package install python3-serial is in the -dev package.

The torch on output needs to be on before an arc ok input can be active. You may be able to test it using a torch pulse user button with a long enough pulse duration.