Finally fix this
I swear if I ever fix this, I'm gonna post a solution. So, here we are. (Error device is corrupt and untrusted)
Bought RM3S from China two weeks ago, don't have a thread now, the phone even comes out tomorrow lol, stumbles here, and can somehow root my phone n all that good stuff. Then, I f-ed up, installing RM3 ROM into RM3S, big mistake I know, somehow I thought it works out. It happens like what some of you experience, non-stop nubia splash screen and looping again n again to fast boot. >> some of the users solve this by going lock>unlock>flash but not for me.
So, after grinding through websites & threads, I concluded one thing. It's the system.img. << this is the one that corrupted and somehow you need to replace it. Then, you look into the rom < there's no system.img. After digging, the system file is somehow related to the file "system.new.dat.br"
So, what you need is to change that ^ into "system.img". To do that, we need to have two things.
*Be warned, don't make mistake like I do, and ensure your rom is correct*
1. You need to have "Brotli", just google it. If you do it right, it will change "system.new.dat.br" into "system.new.dat"
2. Then, you need "sdat2img.py", google it > this thing need some python 2.7+ > and you also need another thing called system.transfer.list from the same rom which add with system.new.dat become output as system.img
3. Then, come to the second problem, the flashing of system.img, the system.img is huge, and your old fastboot will have an error. Go google some latest 2019 adb + fastboot and replaced with your old one. That solved the problem. It will have some magic header warning, but the transfer won't have an error.
4. Reboot, and enjoy your phone escape the boot loop and infinite splash. At least, that what happened to mine. You can flash back twrp and enter it recovery as it meant to be.
I know it's a rough guide, but hey, I hope it help some people out there.