Earlier quoted context omitted.
You can still disable secure boot just fine, just run “csrutil disable” from recovery and the option magically appears. https://support.apple.com/guide/mac-help/macos-recovery-a-ma...
Is it durable or can it be forgotten as a setting? I would be looking at plain Linux boot and erasing Mac os, so any dependency on Mac tools would be nonideal.
Note on those Macs that the security settings are boot volume specific, so that you can have a volume with all security off for fun, and still have a completely secure macOS install selectable via dual-boot.