For your information, if it can help :
I installed Global ROM (xiaomi.eu_multi_MI6_V8.2.25.0.NCACNEC_v8-7.1.zip) with success. But I have the same problem than with my former ROM (China 8.2.26 and CHina 8.2.22).
Actually, the Gear App crashed after cliquing on the "connexion to Gear" button. But I went to the bluetooth management of the Mi6, and I noticed 2 differents S3. A S3 (DCFE) and a S3 (DCFE) LE, the Mi6 can pair one or the other S3.
The pairing code appear on both devices, I accept on the S3 and on the Mi6§. Whatever S3 I pick on the bluetooth interface, I have the pairing code that appears on the watch. After accepting nothing appear on the S3, it is still on the message "Download Gear Apps on your mobile".
The Gear Apps can't be launched once a S3 is paired with the Mi6.
If I unpair the S3 from the phone, the Gear app can be launch again, I can click on the "connect to Gear" button but then, same s**t, the S3 try to connect but after few second the gear App crashes so the connection can't be finalised.
The main problem is that, I think the entire connection can't be made because of the app crash. SO I can see the S3 on the bluetooth interface but as some files should be missing nothing appear on the watch.
I asked samsung but they just say "Device not supported".
Will try the crocobc files. Thank You very much.
EDIT: With your apk crocobc, it works. Great Thanx.