The article is incorrect. You can disable secure boot as simply as clicking an option in a dialog box. https://support.apple.com/en-us/HT208330
According to a thread on /r/linux, disabling secure boot will not allow you to install Linux.
Apple's T2 Will Block Linux from Booting
21–22 of 22 posts
Re: Apple's T2 Will Block Linux from Booting
#22I think articles like this are good even though the solution might be assumed. Getting explicit clarification is what it's all about here. That clarification is that disabling SIP will allow non-signed OSs to boot.
Several users on on StackOverflow and reddit do report that disabling Secure Boot will not allow you to install Linux, only boot a live system.