I also had the problem that arduino-cli includes no serial monitor. I also tried out screen, minicom and other but they are a bit difficult to get used with them. So I created a small python script which works as an serial monitor: https://github.com/PBahner/Serial-Monitor

I also had the problem that arduino-cli includes no serial monitor. I tried out screen, minicom and other but they are a bit difficult to get used with them. So I created a small python script which works as an serial monitor in the command line: https://github.com/PBahner/Serial-Monitor