The old installer had an option to remove all NI Software via the command line:
Automating Uninstallation of NI Software - National Instruments
https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019LfWSAU&l=en-US
While the nipk command line interface has the "remove" option there is no "remove all" feature. It is only possible to remove single packages.
Dr. Christian Neumann
NI Germany
The nipkg.exe help lists the following which supports the ability to remove all packages, see bold text:
nipkg remove [OPTIONS] [PACKAGES]
Uninstalls previously installed package(s).
Use "nipkg remove" to remove all packages except locked and essential
packages and their dependencies.
Use "nipkg remove --force-essential --force-locked" to remove all packages
including locked, essential, and NI Package Manager packages.