I have a Mi 9 and it has been draining battery using the official MIUI 12. I also got a lot of ads in the system apps, which I never can turn off all of them no matter what adblockers I installed. I got frustrated and desperate, so I tried out the famed custom MIUI 12 from Xiaomi.eu. They are very good in extending my battery and so smooth and sleek. I recommend this for other phones too, since this is a custom rom. You wouldn't regret!

So you still maintain the warranty when using the custom MIUI? or just void it altogether?

Warranty is still intact because I didn't open anything. Just unlocking the bootloader wouldn't void warranty as well, but u may need to wait for some time for Xiaomi phones to be unlocked due to their policy. It is very intuitive with its gesture and it has system wide dark mode, how great! It has all the modern features in flagship phones, except changing screen refresh rate as far as I have tried out.

Due to my probation status, I can't reply as often. Hope it helps.

It's the first rom I flashed after getting a K30 Pro Zoom. But heck the bootloader unlocking waiting time was a long one (one week)

Do the local banking apps and e-wallet work on the custom rom? I am using a Redmi Note 4 running the official MIUI 11 (Android 7). Recently, some of the banking apps no longer support Android 7 and wouldn't install on my phone anymore. I don't intend to buy a new phone as I like my Note 4 so am contemplating installing a custom rom.

since xiaomi.eu is sourced from china miui rom (just debloated) the version wont be updated anymore. my redmi note 4x is running on miui10 (android 7) i think thats the final xiaomi.eu rom you can get for this device. so yes netflix and some other banking app like mae wont work on this device.
it's under EOL (End of Life) Devices in xiaomi.eu website already. if you want to use banking apps i suggest you just change to latest budget devices.
if you want to install custom rom you can check xda, but you need to know how to tinker with the device if you want your banking apps to work.

Thanks for your reply. There are several custom roms for Redmi Note 4X (Lineageos, Resurrection Remix, etc) that runs on Android 10. I know that banking apps are sensitive to rooted devices so would like to know if our local banking and ewallet apps have problems installing on custom rom MI devices.

if you run lineageos or other custom rom except xiaomi.eu, unless you use install root with magisk and use magisk hide it will detect custom rom and wont run i think. if you use xiaomi.eu they can pass safety net hence banking apps and such is allowed to use. but problem is the version is too low. so you can look into install android 10 custom rom and magisk hide if you want to use banking apps.

I try to unlock my CN ROM Mi 10 Youth / Zoom but nothing happens when connect to PC during fastboot restart

Yea xiaomi.eu kinda good using their rom for almost 2 year

I recently installed beastos which is based on xiaomi.eu but my banking n e wallet are not working complaining about jailbreak n rooted device. Any help to this?