The Mi Mix 3 5G has had a rocky time of it since its launch last year. Xiaomi launched its first 5G handset on Android 9.0 and MIUI 10 Pie in February 2019, which were the latest versions of Google and Xiaomi's OSes at the time. MIUI 11 then rolled around in October of the same year, but the Mi Mix 3 5G remained on MIUI 10. Xiaomi never brought Android 10 to MIUI 10, so the Mi Mix 3 5G was left stranded on Android 9.0 Pie too.
Following that, Xiaomi began issuing MIUI 12 to devices earlier this year like the Mi 9 and Redmi K20 series. Again, the Mi Mix 3 5G was absent from official release schedules, which remains the case at the time of writing. Despite this, Xiaomi started issuing V12.0.1.0.PEMEUXM to EU handsets at the start of September. Android 9.0 Pie lies at the heart of V12.0.1.0.PEMEUXM but it is a start for the Mi Mix 3 5G, even if it remains on MIUI 10 on the Chinese and global branches of MIUI.
However, there are now reports that V12.0.1.0.PEMEUXM disables 5G connectivity. Xiaomi has yet to comment on the matter, but there are multiple claims that 5G functionality has been removed from the latest EU build for the Mi Mix 3 5G. Some people have verified this by flashing a global build, which requires an unlocked bootloader. Overall, this is the latest example of poor software support for the Mi Mix 3 5G. Xiaomi may eventually upgrade the device to Android 10, but we would not hold out for Android 11.