On my side, I lost the cellular data capabilities by passing from the latest weekly (22.10.26 for cas/Mi10Ultra) to the stable MIUI 14 (V14.0.1.0.TJJCNXM_v14-13). I did a fresh install using fastboot with data format from Windows (probably my first format since MIUI 12 instead of updating the EU rom, awesome work xiaomi.eu team by the way for all those nice past rom updates). The phone can't send or receive international SMS/MMS, but this may also be due to a lock on the cellular provider side (they replaced the old SIM recently, same phone number, but probably different SIM ID). So before initializing MIUI 14, I am welcomed with a prompt saying that the phone is locked and I must log in with my Xiaomi account (I have to connect to wifi first, since there is no cellular data). MIUI 14 is very fluid and nice, but is there a way to get the cellular data capabilities back? I also tried installing the original Xiaomi rom with MiFlash (clean an lock); same data issues on the Chinese rom, Mi-message (or something like that) can't activate, same with the SIM activation (probably due to the international SMS/MMS now being blocked). I unlocked the rom again with miflash unlock (6.6.510.37) and reinstalled the Xiaomi.eu MIUI 14 (in case having the original Xiaomi recovery would help instead of TWRP 3.7.0_12v7.5_A13)... same data issue. Tried an install with TWRP instead of fastboot, same data issue. Tried to roll back to the latest weekly stable with TWRP (A12 this time to match android's version), same data issue. In MIUI, I can't setup a custom APN (this has never been needed, but I wanted to test if entering it manually would help, I made a log of this). Phone calls and national SMS works (inside Norway). With *#*#4636#*#*, my IMEI is there, but the Phone Number informations are empty (no Carrier, UICC, IMS). Any clues on what may be going on?
Edit1: I tried a SIM card from a different carrier (Telenor) and got cellular data with it on MIUI 14 (V14.0.1.0.TJJCNXM_v14-13). The system is fluid and more responsive/snappy than the latest weekly available for Mi10 Ultra. Only the google message app does not work, so I am using the default MIUI messaging app instead. As for why cellular data suddenly stopped working after the update with my current carrier, this remains a mystery. I'm in contact with them to try a different SIM card, and will switch to the other carrier if this does not trouble shoot the data issue. Thanks again Xiaomi.eu team for the good work!
Edit2: There was an issue with the new SIM card, the carrier reactivated the old SIM card and everything is back to normal, with MIUI 14.