I wrote a silly little testcase: https://gist.github.com/jcalvinowens/06530e6fc86f3b2c97a7027...
...but both affected znver5 machines I have "pass", so clearly there's more to it than AMD is telling us.
You should be able to get away with "-march=znver5 -mno-rdrnd -mno-rdseed" in CFLAGS if you care.
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