SUMMARY
I am handling the SIGTSTP signal and hiding the ^Z printout using this script:
$ cat sig.sh 
#!/usr/bin/env bash

# SIGTSTP
trap '' 20
stty -echoctl

echo "before"
sleep 3
echo "middle"
sleep 3
echo "after"

When Ctrl-Z is pressed, konsole emits the visible NULL character with the UTF8 encoding e2 96 92.
The expected outcome is to ignore Ctrl-Z.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: konsole-23.08.5
Qt Version: 5.15.17