I just received my Z9 Mini from Batch 3 ($793, Sep 20 - 30th Batch). US, DHL delivery, no customs.

It seems they have fixed the workaround for overclocking or used a different firmware on this batch that locked down overclocking even more. The filesystem/firmware is dated Fri, August 31st rather than Sun, Aug 12th like Batch 2.
When attempting to use the advanced editor 'F12' and change the frequency manually it just ignores the change and chugs along at 500 freq.

I'm seeing around 11 ksol/s with no OC currently. I'll have to try another work around later like flashing an older version of the firmware.