Thanks a lot for your answer !
I am indeed the nervous type and I am currently doing the backup of the whole device.
I will then follow the guide to root but first, I would like to update to the latest v4 firmware from Onyx, as I am currently on v3.5.4. But the OTA from the device's settings fails.
I have successfully downloaded the firmware from Onyx servers using the following URL: http://data.onyx-international.cn/api/firmware/update?where={%22buildNumber%22:0,%22buildType%22: %22user%22,%22deviceMAC%22:%22%22,%22lang%22:%22en _US%22,%22model%22:%22NoteAir3%22,%22submodel%22:% 22%22,%22fingerprint%22:%22%22}
(Can I ask if you can confirm that it is the right firmware ? Apart from the device name, is there something else I should be careful about, for example if there is different regional versions of the firmwares ?)
And then I have decrypted it using
https://github.com/Hagb/decryptBooxUpdateUpx .
I could do it because I remembered it from the time I rooted my device months ago. But I don't remember how to flash the firmware. What do I do with the decrypted files ? Can they still be flashed through fastboot, or should it be done through EDL now ?
Thanks in advance for any answer, have a nice day !