To disable the pop-up window when opening a SSH-connection on KDEneon first uninstall the ksshaskpass package:

sudo apt purge ksshaskpass

Then comment out all lines in /etc/xdg/plasma-workspace/env/neon_ksshaskpass.sh, so that the file looks like:

#!/bin/sh
# SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
# SPDX-FileCopyrightText: 2025 Carlos De Maine <carlosd.kde@gmail.com>
# export SSH_ASKPASS to be ksshaskpass
 
#export SSH_ASKPASS='/usr/bin/ksshaskpass'
#export SSH_ASKPASS_REQUIRE='prefer'
 
#ssh-add < /dev/null

Finally restart the bash console: exec bash

Sourced partially from: unix.stackexchange.com - How to not use ksshaskpass with SSH