What they're saying there is that when trying to auto detect the server configurations, there are unexpected connections to cloudfare IPs, which didn't usually happen with K9. Who posted the concern associated this to telemetry, but the answers are pointing a different direction. But at this point it just guesses, :(

I guess some more formal traffic inspection needs to happen to understand if truly there's unexpected traffic, where it is directed to, and hopefully infer somehow its purpose. The guesses about what's happening suggest it's just about the auto connection, but again, just guesses.

I explored the configurations, and I didn't find anything about telemetry, and so neither how to disable it. K9 does not have an about:config advanced configuration like desktop Thunderbird does, so if there's truly telemetry or some other sort of information leakage, then after proving it, perhaps developers realize they can do better. But so far nothing really proving telemetry or information leakage.