* Is this the official location to learn of updates, changes etc?
Yes, there in Chineses AppStore, like Mi AppStore.
*Where do you source +86 phone numbers for initial login?
Ask your seller for have an account.
*Looks like firmware 1.10.21 was released today. Upgrading will revert the band back to Chinese correct? So I should wait until a translated version appears here?
Yes it will revert the band to Chinese, so wait I release the Custom English Firmware
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*There appear to be a few spots in the app and in the band that has not been translated yet, are there future plans to progress the translation on those?
The things not translated in the application are webpage, so it can't be translated.
*Any future plans for weather location entries that are local?
By me, I think no. Too much work and modifications for me, also I'm already on some big projects, so I don't have time to look that.
*Any future plans for other payment card services?
Never ^^.