Yesterday I received my buttons, finally turned my phone back, and the first thing I did was install the same crDroid.
It did brick my phone once again.

(more to come...)

At this point, I was very amazed, because that would mean that everything that said @Luisrosso was true, and he hard bricked his phone four times in total, three times with ROMs that I had already installed and played around with.

After the whole evening of experiments, code review, and thinking, I was able to solve this puzzle.

(more to come...)

xiaomi.eu's fastboot script flashes all images to both slots; this is a very clever move by them, so you won't end up accidentally switching slots by flashing Magisk and getting back to the old ROM you had.

The problem is that this Poco has a few bootloader images in the A/B layout, meaning you can have two different bootloaders (simplified, there are many bootloader-related partitions).

Now, every single time (6 times in total), we flashed thought EDL and didn't realize that MiFlash actually flashes only A-Slots and sets them active.
That's why we were able to restore devices as we booted into Slot A after flashing, and that's why every single ROM bricked our device.

(more to come...)

xiaomi.eu's flash script for both of us flashed garbage into bootloader partitions; hence, that's why it broke our phones.
And MiFlash flashed only A slots, leaving broken bootloader partitions in B.
Every single time we flashed custom ROMs, they unpacked themselves into B-slots and made them active.

(more to come...)

What could we do to fix it immediately?
After the first EDL flash, we could flash xiaomi.eu once again, so it'd write working images to both slots, but as we were scared, we didn't do this.
Or we could flash Lineage's copy-partitions zip to duplicate active slots (A) and inactive slots (B).

What can I do as a maintainer of the ROM?
Include flashing firmware into the ROM itself; it should be safer than running Fastboot and would protect from mismatched or broken partitions in the inactive slots.
You also won't need to care about which firmware version you should use with this ROM.

---

Arian, the LineageOS maintainer for this Poco, helped me a lot, and it was essentially his idea about slots that impacted all this.

crDroidAndroid v10.1 Unofficial Alpha QPR1 (Android 14)
for POCO F5 Pro / Redmi K60 (mondrian)

Changelog
* Initial Alpha release
* crDroid 10.1 (https://crdroid.net/blog/2024-01-11-crDroid-10.1-released)
* Android January 2024 Security Update
* Kernel 5.10.189
* Moto Dolby
* EROFS, except for the system partition (remains ext4)

Known problems
* Random stuterrings in the system, would like to get more feedback and logs
* AOD is working only on charging
* FOD icon overlaps bottom text
* FOD enrollment feedback could have visual issues, but it works nevertheless
* More expected to be in Alpha

Telegram group
https://t.me/+REIrxabqqBExOGNi

Download link
https://drive.google.com/file/d/1JSs3Y_5Xi9P9691pVzO922YgMExqbHM1/view?usp=sharing

Please write the most adequate question you'd ask IKEA about this instruction
I'd be happy to hear them all

I am a very proud owner of Nvidia gpu!!!!

I wish whoever made the EU plugs go to hell

Why is this still a problem in 2024?