The paper that I'm seeing only has 4 figures.
In any case, the need for impurities would not itself surprise. Having controlled amounts of impurities is called "doping", it is well-known from studying semiconductors and other high temperature superconductors that the amount of doping can have a huge impact on a substance's properties.
See https://physicsworld.com/a/the-ups-and-downs-of-doping/ for verification of this point.
This is the second, slightly cleaner paper with more figures: https://arxiv.org/ftp/arxiv/papers/2307/2307.12037.pdf
> So, to clarify for my nonexpert brain, if this were a superconductor and their measurements were accurate:
> Fig 5 means the sample must be completely pure to be a superconductor
> The rest of the paper indicates the sample must have impurities.
> So it's pretty safe to say that either it's not a superconductor or their measurements are wrong (or most likely both). Since they never got it to the critical temperature and showed the full Meissner effect, if the measurements are wrong it's fair to say they don't have evidence for superconductivity anyway, just diamagnetism, which isn't really that big a deal
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