I get that, thank you.
But snapshot or not, I think finding an available build that fails for two consecutive releases is a good enough reason to open a post.
Not being able to do that is one of the reasons why I opened the post, I told you, I'm not experienced enough with OpenWrt to do more than what I described in this post.
Trust me I did my best to provide as much information as I could and am open to doing any kind of testing people will suggest to me.
This community has always been helpful and really nice in my posts even when I made silly mistakes, so I want to make things as easy as possible for anyone who could help me.
Reading your three bullet points makes me wonder if you've read my post.
- Not enough experience, have no clue how I can test that
- This is possibly what happened and I evoked two possibles reasons (erase block counter or the linked post)
- I think it's not that as I was able to revert the OEM firmware countless times without any issues and even wrote a post on how to unbrick the device.
As for the forum posts of this device here are all 3 Add support for Redmi AX6 AX3000 Wi-Fi 6 Mesh Router which is closed and redirects to Adding OpenWrt support for Xiaomi AX3600 (Part 1) and General OpenWrt support for Xiaomi AX3600 (Part 2), both are also closed for over 2 months and my issue seems to be less than a month old.
I looked through these forums, tried to ctrl+f to find any info (hate that the forum replaced the browser's search feature...). and couldn't find a clear explanation or solution.
Then I found another person with what seemed to be the same issue Need help installing OpenWrt on Xiaomi Redmi AX6 but it doesn't have any information.
So I decided to open this post to see if maybe I was doing something wrong, if someone already found a workaround, if maybe the tutorial provided on the device page isn't complete anymore or any kind of help.
Before you ask, those reasons are the same for why I didn't open a Github issue first => I'm not confident enough to say that there is a bug in the firmware and am afraid to make devs loose their precious time if I made a silly mistake.
I'm still actively looking for a solution by myself and think I found something that would have to do with a rearrangement of the partitions which would require to flash /dev/mtb11 with a special .itb file or something like that.
For now I don't have a clear tutorial on hand to test this hypothesis, nor am I sure what I found is the root of the problem.
I'm French and my English is probably terrible, so I often make mistakes whether it's in understanding something I read or when writing.
Also, I'm sorry if I made some mistakes in this message or if I sound a little bit too salty (which I am due to those bullet points and the feeling that you didn't read me but I promise this answer isn't here to start a fight or anything bad 
)