should say sudo apt install rather than sudo dpkg --install in Unix Installation Guide for Installing under Debian.
to uninstall:
sudo apt purge dyalog-unicode-200
Please confirm that with Jason.
our docs currently say:
Installing on a DEB-based Linux Distribution
$ unzip linux_64_15.0.26964_unicode.zip
$ sudo dpkg --install linux_64_15.0.26964_unicode.x86_64.deb
That should be updated for version 20.0
There are other mentions of 15.0 on the page as well.