Well here goes these are the steps that worked for me. Hope this helps but I have to say that you follow them at your own risk.
I am certainly no Linux expert and I am using a RPi4 running the latest version of RPi OS.
All the commands following are typed in a terminal window after the $ prompt. I have shown them in large font
Since RPi OS is a version of Debian I followed the steps on the link below for Debian.
If you copy and paste this into your browser it will give more info.
techbase.kde.org/Projects/Edu/KStars/Bui...ing_various_versions
The first thing is to make sure you have all the prerequisites and dependencies.
So open Terminal and type the following command, probably easiest to copy and paste it using the right mouse button. This is all one line it is just wrapping in the viewer.
sudo apt-get -y install build-essential cmake git libeigen3-dev libcfitsio-dev zlib1g-dev libindi-dev extra-cmake-modules libkf5plotting-dev libqt5svg5-dev libkf5xmlgui-dev kio-dev kinit-dev libkf5newstuff-dev kdoctools-dev libkf5notifications-dev qtdeclarative5-dev libkf5crash-dev gettext libnova-dev libgsl-dev libraw-dev libkf5notifyconfig-dev wcslib-dev libqt5websockets5-dev xplanet xplanet-images qt5keychain-dev libsecret-1-dev breeze-icon-theme
You will be asked for your password which in my case was the default
It might ask you to confirm some things as it runs just type Y if prompted.
When it's done you will be returned to the Terminal prompt $
Create and change into a KDE development directory:
mkdir ~/kde && cd ~/kde
Fetch the KStars source code: this site converts links to green characters so make sure that you copy and paste the following line:
git clone anongit.kde.org/kstars
Create and change into a build directory for compilation:
mkdir build && cd build
The next steps will take some time so get a coffee
Run the configure process with cmake:
cmake ../kstars -DCMAKE_INSTALL_PREFIX=/usr
Compile KStars:
make
Install KStars:
sudo make install
Thats it.
To get updates in future its very easy
cd ~/kde/kstars
Git pull —rebase
Good luck