Gadgetbridge

The graphs could indeed use some work, but it pairs just fine with the Mi Band 3 & is available on F-Droid. Also successfully updated my Mi Band 3's firmware with Gadgetbridge, but your mileage may vary.

I liked the statistics charts; they look detailed.

Giving it 4 stars because it did the only thing I wanted it to do, which was sync a Garmin watch to strictly update the time. The app requests an insane amount of permissions, but I can't complain. Uninstalled right after, but very pleased it works.

I believe in Open-Source, but it ask me too many permissions. I understand that most of them are (not)used by different smart devices. But I'm tired of "do not disturb" and "notifications" permissions requiests. I don't want to give them, I just need to correct time on somebody's watches sometimes. But very often I see "All these permissions are required for correct work." and "I want to get access for GPS, phone, calls, sending messages, calendar, contacts, storage". Why so persistently? Thanks to EMUI I can "Disallow and don't ask again" for most of them. But access for "Notifications" and "Do not disturb" is requested on each app startup...

Love it. grapics could be a tad better but it works super with Mi Band 2. Withaout any account.