@kratkale That seems correct to me, yes. If this is a drive you’re testing proof of, I’d first just replace the actual second disk with something you don’t care to lose to test.
What I don’t want is you to just trust me at my word for the sake of things and lose actual data.
Another method you can use in case this isn’t sufficient, it’s a little more involved I suppose is to simply unplug the disk you don’t want being written, but that’s a part of the problem. At a glance you of the hardware you have no idea what drive is which. That’s the basic problem you’re running into now:
nvme0n1 this time might be the right disk, but next boot nvme0n1 might be the student disk. It’s all dependent on who starts up and responds first.