Hello everyone, my first post here. First of all thank you to the developers for providing such a fantastic and versatile tool! 
After trying to launch the serial Monitor in CLion, I noticed something which I feel could be interesting. Indeed, depending on the serial Monitor launch origin, it fails or it succeeds. For example:
(FAILS)
Right clicking the platformio.ini file (or the Tools) menu and then selecting PlatformIO/Monitor, I get an “ioctl error 25” message in CLion “Run” window (see below):
/home/myuser/.platformio/penv/bin/platformio -c clion device monitor -e nodemcuv2 --- Available filters and text transformations: colorize, debug, etc... --- More details at http://bit.ly/pio-monitor-filters Error: (25, 'Inappropriate ioctl for device')
(WORKs)
Now pasting the above first line command …
"/home/myuser/.platformio/penv/bin/platformio -c clion device monitor -e nodemcuv2"
… into CLion’s “Run Anything” command window (accessible via the top right button represented by a small terminal symbol icon or by pressing the CTRL key twice) all works as expected and message displayed in CLion’s “Run” window is:
/home/myuser/.platformio/penv/bin/platformio -c clion device monitor -e nodemcuv2 --- Available filters and text transformations: colorize, etc... --- More details at http://bit.ly/pio-monitor-filters --- Miniterm on /dev/ttyUSB0 115200,8,N,1 --- --- Quit: Ctrl+C | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
It is of course also fine when the above command is used in a Terminal. I hope this help!
My System:
Manjaro Linux with Kernel 5.8.11-1 @ 64 bit
KDE Plasma 5.19.5
CLion 2020.2
PlatformIO core 5.0.2 - Home 3.3.1
My platformio.ini:
[env:nodemcuv2]
platform = espressif8266@2.6.2
board = nodemcuv2
framework = arduino
upload_speed = 460800
upload_port = /dev/ttyUSB0
monitor_port = /dev/ttyUSB0
monitor_speed = 115200