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How to install BricsCAD v13 to V18 on Debian 9 ?
Download and the .deb installer for Debian/Ubuntu. It works fine with Debian 9 Stretch.
Make sure you you have package 'gdebi' installed and start the installation process like this (in a terminal):
You can also configure your file manager to open .deb files with gdebi-gtk (possibly "gdebi-gtk %s") if you don't want to do it from the terminal.