Hey, tested it. Works on my raspi4. No fresh OS install needed, I just updated the raspbian buster with apt-get dist-upgrade as usual.
One small mistake, "./ scadabr.sh" should be "./scadabr.sh".
Before the installation of ScadaBR I changed the listen port of the OpenPLC runtime from 8080->8081 in ~/OpenPLC_v3/webserver/ webserver.py (like Thiago mentioned somewhere):
app.run(debug=False, host='0.0.0.0', threaded=True, port=8081)
Excellent for testing to have OpenPLC and ScadaBR running on one Pi4 now!