Out of interest, for anyone who comes here after reading the title of the thread...
I was lead through the process by an Apple Tech Support person, for my real Mac, and they just use the new Security menu option in Recovery mode.
Generally no need to get bogged-down with Terminal, though obviously if you are confident using it then it's way more powerful and useful.
I think that more cases have common cause now - its the BigSure / filesystem protection. Seems to that without next macos fix the csrutil/recovery console is not working for Silicon platform in order to mount rw the /. Unfortunately it is not always working on Intel Macs and Hacks too. Here is what I have learned trying to narrow some privacy issues of the BigSur, whre you have to alter some files on the system partition to fix that.
Doing some research on "trustd" issue in order to delete the 50 services going fully out of the scope of LULU/LittleSnitch which are specified in the /System/Library/Frameworks/NetworkExtension.framework/Versions/A/Resources/Info.plist.
This one need disabled authenticated-root in order to remove the nasty list compromising you privacy when on VPN. According to my research it is not always working on Intel MacOS by the recovery console.
1. It does not matter you have switched off the Security in the Recovery menu
2. and then in the Terminal changed the SIP by csrutil disable; csrutil authenticated-root disable.
You may not have success on Intel Mac, but definitely it is not working on my new MacBook Air M1 (ok not subj of this forum).
Unfortunately Im not the successful one on the Intels hack. Some are reporting they have success. I had to mount the disk from the other boot disk and then do the change.
Anyways for those who mind it should go like this:
1.Recovery console
2. Terminal: csrutil disable; csrutil authenticated-root disable.
3. (may work) mount -uw /
3b reboot in the MAcOS; (may work) mount -uw /
4. vim /System/Library/Frameworks/NetworkExtension.framework/Versions/A/Resources/Info.plist
5. bless --folder /System/Library/CoreServices --bootefi --create-snapshot
6. potential recovery console with csrutil auth-root back
What has worked for me was the following
1. Boot to other system disk installation
2. Terminal; sudo -i
3. mount -uw /Volumes/MAC - the other system disk where the file shoud be changed
4. vim /Volumes/MAC/System/Library/Frameworks/NetworkExtension.framework/Versions/A/Resources/Info.plist
5. bless --folder /Volumes/MAC/System/Library/CoreServices --bootefi --create-snapshot
6. Reboot to primary system and change firewall rules to block unwanted Apple home calling