There is an english app, and it is perfectly normal for the files to be split. The file size is a limitation of the file system I think.
Here's the app: https://play.google.com/store/apps/details?id=com.xiaomi.xy.sportscamera&hl=en
https://www.amazon.fr/YI-Waterproof-Case-Bo%C3%AEtier-%C3%A9tanche/dp/B01EIYLKRK/ref=aag_m_pw_dp?ie=UTF8&m=A2JAUC835NRI9P This is sold on amazon by YI Europe, don't know if it's legit though..
I started getting the alerts and six second clips in the Yi app again yesterday (03/02/19) afternoon. Also getting them today when testing.
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Also got a reply from Yi Support:
Thank you for contacting YI Tech support.
As of 3/1/2019, there has been an update to the Yi home app. We do know that the performance of the app has not been great over the last few weeks but we have already gotten positive feedback from other users of it working successfully. Currently, this update is for Android only and can be found at the link below, as for iOS the app should be coming within the next few days after it completes the review process by Apple. If you are updating the app on Android please let us know how it is working for you. Your feedback is crucial so that way we can be sure it was a success.
Thank you for your patience
Best Regards,
Chris
Yi Customer Support
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Couldn't you get a case with a hot shoe adapter on top and then use that with an external. Something like this?
Yes they are! These are the ones that I purchased when I ordered my Yi Lite. They only Mention the 4k/4k+ but they work like a charm.
https://smile.amazon.com/gp/product/B01HM8L0Z6/ref=oh_aui_detailpage_o06_s01?ie=UTF8&psc=1
One manufacturer includes a key (see: https://www.amazon.com/manual-focus-PixAero-lens-Plus/dp/B075TCS16D). Here's the installation video (make sure to use CC for english subtitles): https://www.youtube.com/watch?v=xTVGA66HFS8
You have to use their app to stream. This means that you will have to leave a phone by the camera at all times.
This is the app you need to use.
If you want to leave your house and still watch it this means you need another phone, as you have to leave one at home by your printer, and I assume you always bring your phone with you.