bring up a terminal (or konsole in kde) and run the following commands one at a time:
pamac install inkscape
That will install inkscape
inkscape
That will start an inkscape session. Run through all the “next, next” bits until you get to start a new document. Then close inkscape and run the following commands:
wget https://github.com/inkstitch/inkstitch/releases/latest/download/inkstitch-2.2.0-linux.sh
That will download the most recent version of the inkstitch install script
sh ./inkstitch-2.2.0-linux.sh
That will install the inkstitch install script that we just downloaded.
You are now finished. Start an inkscape session and confirm that inkstitch is in the extensions menu.