Unable to set dtr: true on Linux since upgrade to v9.0.7 (other platforms unaffected)

[GazHank]

Summary of Problem

(Please answer all 3)

• What are you trying to do? set dtr: true, pause then set dtr: false in order to invoke a bootloader mode
• What happens? On Linux since version v9 no dtr setting change occurs, it works fine on v8.0.8; and works correctly on win10 for both v9 and v8
• What should have happened? setting dtr true works successfully on windows and mac using v9, however it only seems to work on Linux up to v8.0.8

Code to Reproduce the Issue

const port = new SerialPort(path)

<code to connect to the relevant port>

port.set({ dtr: true }, async () => {
  await this.delay(1000);
  port.set({ dtr: false }, async () => {
    console.log("waiting for bootloader");
    ...<code to detect bootloader status or error out>...
  }
}

Versions, Operating System and Hardware

• SerialPort@v9 (works on v8)
• Node.js v14
• Linux Ubuntu 20.04.2 LTS 64bit (works on Windows & Mac) - I've also had similar reports from others running other linux distros
• Hardware and chipset? (attempting to send dtr to arduino:samd)

[GazHank]

It appears that any attempt to set dtr on Linux with Serialport v9 results in a port error "Error: Error: Operation not supported, cannot set". The exact same operation works on v8 (up to and including 8.0.8). It also works correctly on WIndows 10 for both v8 and v9.

I've created a tweaked version of the electron-serialport example to demonstrate the issue

version info with issues:

• Node.js 14.16.0
• Chromium 89.0.4389.128
• Electron 12.0.5
• Serialport 9.0.7

version info without issues:

• Node.js 14.16.0
• Chromium 89.0.4389.128
• Electron 12.0.5
• Serialport 8.0.8

[GazHank]

Closing this issue as #2240 more clearly explains the issue