It’s an option during bootup that disables restricted/multiverse. Instructions to use do it are  and all it really does is . The intent (in my understanding) is to give a user a quick way to say “we don’t want to see” any proprietary software.
This doesn’t work for several reasons:
- If you are really trying to do no firmware/microcode - this doesn’t work as some - microcode is not mostly included in main (blame spectre if you must)
- All Snaps show up (which we should give an open source only option - but I’ll leave that to the other thread)
Does anyone still use it? If so, what’s your motivation?
 see full instructions on the QA page: http://iso.qa.ubuntu.com/qatracker/milestones/397/builds/182644/testcases/1307/results
 apt-setup/restricted=false apt-setup/multiverse=false
This is the equivalent of enabling the “Free Software Only” boot mode. This will disable the restricted and multiverse repositories at the earliest stages of the debian-installer. This can be helpful is you don’t need them at all or don’t mirror those repositoriesat your local mirror.’