I opened a case with Meraki support and asked them convert my 9164 AP to DNA-C mode (basically the traditional Cisco AP mode where the AP connects to a Cat9800 WLC). After a couple emails back and forth proving the AP was really mine, they converted it. Took about a day from the time I opened the ticket. Once that happened, the AP connected to my 9800 WLC, upgraded code, and then I was able to convert it into Cisco survey mode. I'm happy to report that the 6GHz radio comes up fine when the AP is in traditional Cisco mode. So this is definitely a Meraki bug.
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